JP2011238982A - Communication device, ring-shaped transmission path system, and transmission direction switching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication device which makes use of a transmission route with an existing protocol by realizing switch-over of transmission direction without adding a new control line.SOLUTION: A communication device transmits a direction switch-over command from a first input and output terminal, which is one of two input and output terminals, to a ring-shaped transmission path (S12), receives the direction switch-over command, which has circled the ring-shaped transmission path once, from a second input and output terminal, which is the other of two input and output terminals (S14), and after receiving it, controls the switch-over of two input and output terminals in such a way that the transmission direction between two input and output terminals and the ring-shaped transmission path will be reversed compared to the time before the direction switch-over command has been transmitted (S16).

Description

  The present invention relates to a communication device, a ring-shaped transmission line system, and a transmission direction switching method in a network system in which a plurality of devices are connected in a ring shape.

  In a network system in which multiple devices are connected in a ring shape, when data is transmitted from a source device (called a host device) to a destination device (slave device), it passes through other devices on the path. It is necessary to let When data passes through another device, power corresponding to the transmission protocol is consumed, so that the ring-shaped transmission path system has a problem that power consumption for transmission tends to increase.

In order to realize this, a technique for switching the transmission direction of the ring-shaped transmission path is necessary.
There is Patent Document 1 as a conventional technique for switching the transmission direction of a ring-shaped transmission path.

  Patent Document 1 describes a method of adding a control line related to transmission and switching the transmission direction between a host device and a slave device. Power consumption is reduced by switching the transmission direction so that the transmission path is shortened.

JP-A-5-67021

  However, in the prior art, since a new control line is added to control the transmission direction, there is a problem that the mounting cost as a system increases. Further, when a ring-shaped network system is constructed by utilizing a transmission path of an existing protocol, there is a problem that it is impossible to cope with the conventional technology because addition of a control line is not allowed.

  The present invention has been made in view of the above problems, and realizes switching of a transmission direction without adding a new control line, and a communication device, a ring-shaped transmission line system, and a transmission that utilize a transmission path of an existing protocol. An object is to provide a direction switching method.

  A communication device according to an aspect of the present invention is a communication device connected to a ring-shaped transmission path, and is connected to the ring-shaped transmission path and is capable of switching between input and output, and the ring-shaped transmission path. A command generation unit that generates a direction switching command that instructs all other communication devices to switch the transmission direction of the transmission path; and a control unit that controls the two input / output terminals and the command generation unit. The control unit causes the direction switching command to be transmitted from the first input / output terminal, which is one of the two input / output terminals, to the ring-shaped transmission path, and the direction switching is performed once around the ring-shaped transmission path. When a command is received from a second input / output terminal that is the other of the two input / output terminals, the transmission direction between the two input / output terminals and the ring-shaped transmission line is set to the direction switching command. The switching of the two input / output terminals is controlled so as to be inverted compared with that before transmission.

  According to this configuration, the switching of the transmission direction of the ring-shaped transmission path can be realized by causing the direction switching command to make one round of the ring-shaped transmission path. That is, it is possible to easily switch the transmission direction by utilizing an existing ring-shaped transmission path without adding a new control line.

  Here, the communication device further includes a state determination unit that determines whether the two input / output terminals can be switched based on an operation state of the communication device, and the control unit includes the state determination unit. The direction switching command may be transmitted from the first input / output terminal when it is determined that can be switched.

  According to this configuration, it is possible to reduce the performance degradation of the communication device due to the switching of the transmission direction by determining the operation state of the communication device (for example, the state where the processing load is light or the standby state), and consequently the switching of the transmission direction. Degradation of the transmission performance of the ring-shaped transmission line can be reduced.

  Here, the communication device further includes a state determination unit that determines whether the two input / output terminals can be switched based on an operation state of the communication device, and the control unit includes the ring-shaped transmission. The two input / output terminals and the ring-shaped transmission path when the direction switching command that has made a round of the path is received from the second input / output terminal and the state determination unit determines that the switching is possible. The two input / output terminals may be controlled so as to reverse the transmission direction between the two.

  According to this configuration, it is possible to reduce the performance degradation of the communication device due to the switching of the transmission direction by determining the operation state of the communication device (for example, the state where the processing load is light or the standby state), and consequently the switching of the transmission direction. Degradation of the transmission performance of the ring-shaped transmission line can be reduced.

  Here, the control unit further transmits the direction switching command from the first input / output terminal to the ring-shaped transmission line, and then switches the first input / output terminal from an output to an input. Whether or not a switching completion notification indicating that transmission direction switching has been completed is received from the first input / output terminal within a first predetermined time from transmission of the direction switching command from the adjacent communication device on the transmission path If it is determined that the switch completion notification has not been received within the first predetermined time, it is determined that the transmission direction has failed and the first input / output terminal is output from the input. In the case where it is determined that the completion notification is received within the first predetermined time, it may wait for the direction switching command to be received from the second input / output terminal.

  According to this configuration, since the notification of switching completion is received from the adjacent communication device, it is possible to easily determine whether transmission direction switching is successful.

  Here, the control unit further transmits the direction switching command from the first input / output terminal to the ring-shaped transmission path, and then switches the transmission direction in any communication device on the ring-shaped transmission path. It is determined whether or not a switching failure notification indicating failure has been received from the first input / output terminal. When the switching failure notification is received, it is determined that transmission direction switching has failed, and the 2 One of the two input / output terminals may be returned from the input to the output.

  According to this configuration, since the switching failure notification is received from the adjacent communication device, it is possible to detect the success or failure of switching of the transmission direction.

  Here, when the switching failure notification is received, the control unit may further identify a communication device that has failed to switch the transmission direction based on a transmission source address of the switching failure notification.

  According to this configuration, since the communication device that has failed to switch the transmission direction is identified, for example, the failed communication device can be identified.

  Here, the control unit switches the second input / output terminal from the input to the output when the direction switching command that makes one round of the ring-shaped transmission line is received from the second input / output terminal. May be.

  According to this configuration, it is possible to easily switch the transmission direction and detect a failed communication device by using an existing ring transmission path without adding a new control line.

  The communication device according to an aspect of the present invention is a communication device connected to a ring-shaped transmission path, and is connected to the ring-shaped transmission path and can be switched between input and output, Whether the command is a direction switching command for instructing switching of the transmission direction of the ring-shaped transmission line by analyzing a command received from the first input / output terminal which is one of the two input / output terminals. A command analysis unit for determining whether or not the command received from the first input / output terminal is the direction switching command, the direction switching command is the other of the two input / output terminals. A control unit that transmits from the second input / output terminal and switches between the input and output of each of the two input / output terminals is provided.

  According to this configuration, when the direction switching command is received, it is further transferred to the downstream communication device, and the input and output of each of the two input / output terminals are switched. Therefore, the direction switching command is transmitted along the ring-shaped transmission line. It is possible to easily realize one round and easily switch the transmission direction by utilizing an existing ring-shaped transmission path without adding a new control line.

  Here, the communication device further includes a state determination unit that determines whether or not the two input / output terminals can be switched based on an operation state of the communication device, and the control unit includes the first determination unit. When it is determined that the command received from the input / output terminal is the direction switching command and the state determination unit determines that switching is not possible, the state determination unit waits for the determination to change and waits for a certain period of time. Then, after the determination is changed to be switchable, the direction switching command may be transmitted from the second input / output terminal to switch between the input and output of each of the two input / output terminals.

  According to this configuration, it is possible to reduce the performance degradation of the communication device due to the switching of the transmission direction by determining the operation state of the communication device (for example, the state where the processing load is light or the standby state), and consequently the switching of the transmission direction. Degradation of the transmission performance of the ring-shaped transmission line can be reduced.

  Here, the communication device further includes a notification generation unit that generates a switching completion notification indicating that the switching of the output and input of the two input / output terminals is completed according to the direction switching command, and the control unit includes: After completion of switching between the input and output of each of the two input / output terminals, a switching completion notification generated by the notification generation unit may be transmitted from the first input / output terminal.

  According to this configuration, since the switching completion notification is transmitted to the communication device that is the transmission source of the direction switching command, it is possible to easily determine whether the transmission direction switching is successful.

  Here, the control unit indicates a switch completion notification indicating that the transmission direction switching has been completed in the adjacent communication device within a second predetermined time from the transmission of the direction switch command from the second input / output terminal. Is received from the second input / output terminal, and the notification generation unit further determines that the switch completion notification is not received within the second predetermined time, the adjacent communication device Generates a switching failure notification indicating that the switching of the transmission direction has failed, and the control unit further causes the switching failure notification generated by the notification generation unit to be transmitted from the first input / output terminal. The input and output of each of the two input / output terminals may be returned to the same state as before receiving the direction switching command.

  According to this configuration, since the switching failure notification is received from the adjacent communication device, it is possible to detect the success or failure of switching of the transmission direction.

  Here, the notification generation unit may generate the switching failure notification including the address of the communication device.

  According to this configuration, it is possible to easily identify the communication device that has failed to switch the transmission direction, for example, it is possible to identify the failed communication device.

  Here, the control unit determines whether or not a switching failure notification indicating that the switching of the transmission direction has failed in any communication device on the ring-shaped transmission path is received from the second input / output terminal. When it is determined that the switching failure notification is received from the second input / output terminal, the switching failure notification is transmitted from the first input / output terminal, and the two input / output terminals receive the direction switching command. You may make it return to the same state as before.

  According to this configuration, since the switching failure notification is sequentially transferred by a plurality of communication devices on the ring-shaped transmission path, for example, a failed communication device can be easily identified.

  A ring-shaped transmission line system according to one embodiment of the present invention is a ring-shaped transmission line system including a host device connected to the ring-shaped transmission line and a plurality of slave devices. The host device instructs two other host I / O terminals connected to the ring-shaped transmission line and capable of switching between input and output, and all other slave devices to switch the transmission direction of the ring-shaped transmission line. A command generation unit that generates a direction switching command; and a host control unit that controls the two host I / O terminals and the command generation unit. The host control unit causes the direction switching command to be transmitted from the first host I / O terminal, which is one of the two host I / O terminals, to the ring-shaped transmission path, and the ring-shaped transmission path is set to 1 When the rotated direction switching command is received from a second host I / O terminal which is the other of the two host I / O terminals, the two host I / O terminals, the ring transmission line, The switching of the two host I / O terminals is controlled so that the transmission direction between the two is reversed compared to before the transmission of the direction switching command. Each slave device has two slave I / O terminals connected to the ring-shaped transmission line and capable of switching between input and output, and a first slave I / O which is one of the two slave I / O terminals. Analyzing the command received from the O terminal to determine whether the command is a direction switching command for instructing switching of the transmission direction of the ring-shaped transmission path; and the first slave. When it is determined that the command received from the I / O terminal is the direction switching command, the direction switching command is transmitted from the second slave I / O terminal which is the other of the two slave I / O terminals. And a slave control unit for switching between input and output of each of the two slave I / O terminals.

  According to this configuration, when each slave device receives the direction switching command, it forwards it to a further downstream communication device and switches between the input and output of each of the two slave I / O terminals. It is possible to easily realize one round along the ring-shaped transmission path, and to easily switch the transmission direction by utilizing the existing ring-shaped transmission path without adding a new control line. . The host device can switch the transmission direction of the ring-shaped transmission line by rotating the direction switching command once around the ring-shaped transmission line. That is, it is possible to easily switch the transmission direction by utilizing an existing ring-shaped transmission path without adding a new control line.

  Here, the host device further includes a host state determination unit that determines whether the two host I / O terminals can be switched based on an operation state of the host device, and the host control unit includes: When the host state determination unit determines that the switching is possible, the direction switching command is transmitted from the first host I / O terminal, and each slave device is further configured based on the operation status of the slave device. A slave state determination unit that determines whether or not two slave I / O terminals can be switched; and the slave control unit is configured such that a command received from the first slave I / O terminal is the direction switching command. When it is determined that the slave state determination unit determines that switching is not possible, the slave state determination unit waits for the determination to change, and the determination is made within a certain time. After changes possible exchange, and it sends the direction switching command from said second slave I / O terminals, may be switched between the output and the two slave I / O pins each input.

  According to this configuration, it is possible to reduce the performance degradation of the host device due to the switching of the transmission direction by determining the operation status of the host device and each of the slave devices (for example, a light processing load state or a standby state). It is possible to reduce deterioration in transmission performance of the ring-shaped transmission line due to switching of the transmission direction.

  Here, the host control unit further transmits the direction switching command from the first host I / O terminal to the ring-shaped transmission line, and then inputs the first host I / O terminal from an output. And a switching completion notification indicating that transmission direction switching has been completed from an adjacent slave device on the ring-shaped transmission path is transmitted within a first predetermined time from the transmission of the direction switching command. It is determined whether or not it has been received from the O terminal, and if it is determined that the switch completion notification has not been received within the first predetermined time, it is determined that transmission direction switching has failed and the first When the host I / O terminal is returned from the input to the output and it is determined that the completion notification is received within the first predetermined time, the direction switching command is received from the second host I / O terminal. Wait for The slave device further includes a notification generation unit that generates a switching completion notification indicating that switching between output and input of the two slave I / O terminals is completed according to the direction switching command, and the slave control unit includes: After completion of switching between the input and output of each of the two slave I / O terminals, a switching completion notification generated by the notification generation unit may be transmitted from the first slave I / O terminal.

  According to this configuration, since the slave device transmits a switch completion notification to the host device that is the transmission source of the direction switching command, the host device can easily determine the success or failure of the transmission direction switching.

  Here, the host control unit further transmits the direction switching command from the first host I / O terminal to the ring-shaped transmission path, and then switches the transmission direction in the slave device on the ring-shaped transmission path. It is determined whether a switching failure notification indicating failure has been received from the first host I / O terminal. If the switching failure notification is received, it is determined that switching of the transmission direction has failed, The one of the two host I / O terminals is returned from the input to the output, and the slave control unit, within a second predetermined time from the transmission of the direction switching command from the second slave I / O terminal, It is determined whether or not a switch completion notification indicating that transmission direction switching has been completed in the adjacent host device is received from the second slave I / O terminal, and the notification generator further includes the second Predetermined If it is determined that the switching completion notification has not been received within a short time, a switching failure notification indicating that the adjacent slave device has failed to switch the transmission direction is generated, and the slave control unit further generates the notification The switching failure notification generated by the unit is transmitted from the first slave I / O terminal, and the input and output of each of the two slave I / O terminals are returned to the same state as before receiving the direction switching command. May be.

  According to this configuration, since the switching failure notification is transmitted from the slave device adjacent to the slave device that has failed to be switched, the host device can easily detect the success or failure of switching of the transmission direction.

  Here, the notification generation unit generates the switching failure notification including an address of its own slave device, and the host control unit further transmits a source of the switching failure notification when the switching failure notification is received. You may make it identify the slave apparatus which failed to switch the transmission direction based on the address.

  According to this configuration, it is possible to easily identify the slave device that failed to switch the transmission direction, for example, to identify the failed host device.

  Here, the slave control unit determines whether or not a switching failure notification indicating that the switching of the transmission direction has failed in any slave device on the ring-shaped transmission path is received from the second slave I / O terminal. If the switch failure notification is received from the second slave I / O terminal, the switch failure notification is transmitted from the first slave I / O terminal, and the two slave I / O terminals are transmitted. The / O terminal may be returned to the same state as before receiving the direction switching command.

  According to this configuration, since the switching failure notification is sequentially transferred by a plurality of host devices on the ring-shaped transmission path, for example, a failed host device can be easily identified.

  Further, a transmission direction switching method for a ring-shaped transmission line according to one aspect of the present invention is a transmission direction switching method for a ring-shaped transmission line including a host device and a plurality of slave devices connected to the ring-shaped transmission line, The host device has two host I / O terminals that are connected to the ring-shaped transmission line and can be switched between input and output, and each slave device is connected to the ring-shaped transmission line and can be switched between input and output. The transmission direction switching method generates a direction switching command for instructing all other slave devices to switch the transmission direction of the ring-shaped transmission path in the host device, In the host device, the direction switching command is sent from the first host I / O terminal which is one of the two host I / O terminals to the ring-shaped transmission line. And the host device receives the direction switching command that makes one round of the ring-shaped transmission line from a second host I / O terminal that is the other of the two host I / O terminals, and In the apparatus, when the direction switching command is received, the transmission direction between the two host I / O terminals and the ring-shaped transmission path is reversed as compared with before transmission of the direction switching command. Controls switching of two host I / O terminals.

  According to this configuration, the switching of the transmission direction of the ring-shaped transmission path can be realized by causing the direction switching command to make one round of the ring-shaped transmission path. That is, it is possible to easily switch the transmission direction by utilizing an existing ring-shaped transmission path without adding a new control line.

  As described above, in one embodiment of the present invention, the transmission direction is switched without adding a transmission control line by switching the transfer direction using the direction switching command for switching the transmission direction. This direction switching command is issued by a communication device (for example, a host device) that requests switching of a transmission path. This direction switching command is a simple command that can instruct direction switching to all other communication devices (for example, slave devices) at once, and can also reduce power consumption required for switching the transmission direction.

  As described above, according to the present invention, it is possible to easily switch the transmission direction by utilizing an existing ring-shaped transmission path without adding a new control line.

It is a figure which shows the structure of one Embodiment of the system which concerns on this invention. It is a figure which shows the structure of the ring-shaped transmission-line system of 1st Embodiment concerning this invention. It is a figure which shows 1 structure of a packet format. It is a figure which shows the structure of the host apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the slave apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the switching process of the transmission direction of the ring-shaped transmission line which concerns on the 1st Embodiment of this invention in time series. It is a figure which shows the input / output state (I / O terminal 205: input, I / O terminal 206: output) of the host apparatus based on the 1st Embodiment of this invention. It is a figure which shows the input / output state (I / O terminal 205: input, I / O terminal 206: input) of the host apparatus based on the 1st Embodiment of this invention. It is a figure which shows the input / output state (I / O terminal 205: Output, I / O terminal 306: Input) of the host apparatus based on the 1st Embodiment of this invention. It is a figure which shows the input / output state (I / O terminal 305: input, I / O terminal 306: output) of the slave apparatus based on the 1st Embodiment of this invention. It is a figure which shows the input / output state of the slave device which concerns on the 1st Embodiment of this invention (I / O terminal 305: output, I / O terminal 306: output). It is a figure which shows the input / output state (I / O terminal 305: output, I / O terminal 306: input) of the slave apparatus based on the 1st Embodiment of this invention. It is a figure which shows the operation | movement process sequence at the time of the transmission direction switch of the host apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the operation | movement process sequence at the time of the transmission direction switch of the slave apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the ring-shaped transmission-line system which concerns on the 2nd Embodiment of this invention. It is a figure which shows the case where the transmission direction is normally switched based on the 2nd Embodiment of this invention in time series. It is a figure which shows the case where the transmission direction which concerns on the 2nd Embodiment of this invention is not switched in time series. It is a figure which shows the structure of the host apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the slave apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the operation | movement process sequence at the time of the transmission direction switch of the host apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the operation | movement process sequence at the time of the transmission direction switching process of the slave apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the ring-shaped transmission-line system which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structure of the host apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structure of the slave apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows the case where the transmission direction is normally switched based on the 3rd Embodiment of this invention in time series. It is a figure which shows the case where the transmission direction which concerns on the 3rd Embodiment of this invention cannot be switched in time series.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
There are two types of communication devices in the present embodiment: a communication device as a host device and a communication device as a slave device.

  The communication device as the host device includes two host I / O terminals (I / O is an abbreviation of input / output) that are connected to the ring-shaped transmission line and can be switched between input and output, and the ring-shaped transmission line A command generation unit that generates a direction switching command that instructs all other slave devices to switch the transmission direction, and a host control unit (200) that controls the two host I / O terminals and the command generation unit. The host control unit causes the direction switching command to be transmitted from the first host I / O terminal, which is one of the two host I / O terminals, to the ring-shaped transmission line (S12), and the ring-shaped transmission is performed. When the direction switching command that makes a round of a path is received from a second host I / O terminal that is the other of the two host I / O terminals, the two host I / O terminals and the ring shape The switching of the two host I / O terminals is controlled so as to reverse the transmission direction to and from the transmission path as compared to before the transmission of the direction switching command.

  The communication device as a slave device is a first slave which is one of the two slave I / O terminals connected to the ring-shaped transmission line and capable of switching between input and output, and the two slave I / O terminals. Analyzing the command received from the slave I / O terminal to determine whether or not the command is a direction switching command instructing switching of the transmission direction of the ring-shaped transmission path; When it is determined that the command received from one slave I / O terminal is the direction switching command, the direction switching command is sent to the second slave I / O terminal which is the other of the two slave I / O terminals. And a slave control unit (control unit 301) that switches between input and output of each of the two slave I / O terminals.

  This makes it easy to make a direction switch command once along the ring-shaped transmission path, and switch the transmission direction by using an existing ring-shaped transmission path without adding a new control line. It can be easily realized.

FIG. 1 shows the configuration of one embodiment of a system according to the present invention.
The LSI 11 shown in FIG. 1 includes a CPU 12, a host device 1, and a bus 13 as a part of the LSI 11. The host device 1 receives a command from the CPU 12 via the bus 13, and a plurality of slave devices 2 to N (N is Provide a function as a controller to control (integer). Note that the host device may be provided as a specific LSI, or may be provided as an LSI including a CPU and a bus. The slave devices 2 to N include a controller function and a storage area. The storage area included in the slave devices 2 to N may be an input / output interface circuit with the external device 14.

  FIG. 2 shows a configuration of a ring-shaped transmission line system 10 in which the host device 1 and the slave devices 2 to N shown in FIG. 1 are connected in a ring shape. In FIG. 2, one host device 1 and a plurality of slave devices 2 to N operating under the control of the host device 1 are sequentially connected by a ring-shaped transmission line, and packets are transmitted in one direction. The host device 1 and the slave devices 2 to N have addresses that can be uniquely identified on the ring-shaped transmission line system 10. The direction of the arrow shown in FIG. 2 indicates the data transfer direction of the ring-shaped transmission line system 10. A solid line arrow indicates that the data is transferred in a counterclockwise direction, and a broken line arrow indicates that the data is transferred in a clockwise direction.

  FIG. 3 shows one configuration example of a format of a packet in which the host device 1 and the slave devices 2 to N communicate on the ring transmission line system 10.

  The packet format 40 includes a data type part 41, a transmission source address part 42, a transmission destination address part 43, and a data part 44.

  The data type part 41 indicates whether the packet is a command or data. The transmission source address section 42 indicates the address of a device that transmits a packet. The transmission destination address section 43 indicates the address of a device that is a packet destination. In the data portion 44, when the data type portion 41 indicates a command, a write command or a read command is set, and when the data type portion 41 indicates data, data such as a still image or a moving image is set.

  When the host device 1 communicates with any one of the slave devices 2 to N on a one-to-one basis, the address of the host device 1 is set as the transmission source address, and the address of the slave device to be communicated is set as the transmission destination address. To do.

FIG. 4 shows the configuration of the host device 1.
The host device 1 includes a control unit 200 that controls the operation of the host device 1 (the host control unit described above), a command generation unit 201 that generates commands, a command analysis unit 202 that analyzes commands, and a ring-shaped transmission line. Connected I / O terminals 205 and 206, an input / output switching control unit 204 that controls switching of input and output of the I / O terminals 205 and 206, direction switching buffers 207 to 210, an input buffer 211, and an output buffer 212. The control unit 200 includes a state determination unit 203 that determines the operation state of the host device 1. Note that the first host I / O terminal is one of the I / O terminals 205 and 206 (for example, a terminal set to “output”), and the second host I / O terminal is the I / O terminal 205, The other of 206 (for example, a terminal set to “input”).

  The control unit 200 controls the overall operation of the host device 1. Based on the information of the state determination unit 203, the control unit 200 notifies the command generation unit 201 and the input / output switching control unit 204 described later of the control information.

  Upon receiving control information from the control unit 200, the command generation unit 201 generates a command conforming to the packet format 40 based on the control information.

  The command analysis unit 202 analyzes the command received by the host device 1 from the ring-shaped transmission line into the input buffer, and notifies the control unit 200 of the analysis result.

  The state determination unit 203 determines whether the input / output of the I / O terminals 205 and 206 can be switched based on the operation status of the host device 1.

  The input / output switching control unit 204 sets the voltage of the input / output switching control lines 213 and 214 to a high level (H) or a low level according to control information from the command generation unit 201 or control information from the control unit 200. Control to (L).

Direction switching buffers 207 and 208 are connected to the I / O terminal 205.
The direction switching buffers 207 and 208 are either in a conductive state or a cut-off state depending on the voltage level of the input / output switching control line 213. When the voltage of the input / output switching control line 213 is at a high level (H), the direction switching buffer 207 is turned on and the direction switching buffer 208 is turned off. As a result, the I / O terminal 205 is connected to the input buffer 211 and becomes an input terminal. When the voltage of the input / output switching control line 213 is at a low level (L), the direction switching buffer 207 is cut off and the direction switching buffer 208 is turned on. As a result, the I / O terminal 205 is connected to the output buffer 212 and becomes an output terminal.

Direction switching buffers 209 and 210 are connected to the I / O terminal 206.
The direction switching buffers 209 and 210 have the same functions as the direction switching buffers 207 and 208 described above. When the voltage of the input / output switching control line 214 is at a high level (H), the direction switching buffer 209 is turned on and the direction switching buffer 210 is turned off. As a result, the I / O terminal 206 is connected to the output buffer 212 and becomes an output terminal. When the voltage of the input / output switching control line 214 is at a low level (L), the direction switching buffer 209 is cut off and the direction switching buffer 210 is turned on. As a result, the I / O terminal 206 is connected to the input buffer 211 and becomes an input terminal.

  As described above, the host device 1 can switch the input and output of the I / O terminals 205 and 206 by controlling the voltages of the input / output switching control lines 213 and 214 from the input / output switching control unit 204.

FIG. 5 shows a configuration of the slave device m (m is an arbitrary natural number of 2 ≦ m ≦ n).
The slave device m includes a functional unit 300, a control unit 301 that controls the operation of the slave device m (the slave control unit described above), a command analysis unit 302 that analyzes a command, and an I / O connected to the ring-shaped transmission line. The input / output switching control unit 304 for controlling input / output switching of the O terminals 305 and 306, the I / O terminals 305 and 306, direction switching buffers 307 to 310, an input buffer 311, and an output buffer 312. . The control unit 301 includes a state determination unit 303 that determines the operation state of the slave device m. Note that the first slave I / O terminal is one of the I / O terminals 305 and 306 (for example, the terminal set to “output”), and the second slave I / O terminal is the I / O terminal 305, The other of 306 (for example, a terminal set to “input”).

  The functional unit 300 is a memory or an I / O device including a storage area. Alternatively, the functional unit 300 includes an I / F that performs input / output control with an external device.

  The control unit 301 controls the overall operation of the slave device m. The control unit 301 notifies the input / output switching control unit 304 described later of the control information based on the information of the state determination unit 303. In addition, the control unit 301 notifies the command analysis unit described later of control information for transferring the received command.

  The command analysis unit 302 analyzes the command received by the slave device m and notifies the control unit 301 of the analysis result.

  The state determination unit 303 determines whether the input / output of the I / O terminals 305 and 306 can be switched based on the operation status of the slave device m.

  The input / output switching control unit 304 controls the voltage of the input / output switching control lines 313 and 314 to a high level (H) or a low level (L) according to control information from the control unit 301.

Direction switching buffers 307 and 308 are connected to the I / O terminal 305.
The direction switching buffers 307 and 308 are either in a conduction state or a cutoff state depending on the voltage level of the input / output switching control line 313. When the voltage of the input / output switching control line 213 is at a high level (H), the direction switching buffer 307 is turned on and the direction switching buffer 308 is turned off. As a result, the I / O terminal 305 is connected to the input buffer 311 and becomes an input terminal. When the voltage of the input / output switching control line 313 is at a low level (L), the direction switching buffer 307 is cut off and the direction switching buffer 308 is turned on. As a result, the I / O terminal 305 is connected to the output buffer 312 and becomes an output terminal.

Direction switching buffers 309 and 310 are connected to the I / O terminal 306.
The direction switching buffers 309 and 310 have the same function as the direction switching buffers 307 and 308 described above. When the voltage of the input / output switching control line 314 is at a high level (H), the direction switching buffer 309 is turned on and the direction switching buffer 310 is turned off. As a result, the I / O terminal 306 is connected to the output buffer 312 and becomes an output terminal. When the voltage of the input / output switching control line 314 is at a low level (L), the direction switching buffer 309 is cut off and the direction switching buffer 310 is turned on. As a result, the I / O terminal 306 is connected to the input buffer 311 and becomes an input terminal.

  As described above, the slave device m can switch the input and output of each of the I / O terminals 305 and 306 by controlling the voltage of the input / output switching control lines 313 and 314 from the input / output switching control unit 304.

Next, the operation of switching the transmission direction of the ring transmission line system 10 will be described.
The transmission direction of this ring-shaped transmission line is switched by the host device and the slave device using the direction switching command which is an instruction to switch the input / output of the I / O terminal. This is realized by sequentially switching the. This ring-shaped transmission line has the following characteristics.

  (A) The host device transmits a direction switching command to the next slave device connected in the transmission direction. When the slave device receives the direction switching command, the slave device transfers the direction switching command to the next slave device, and switches the input / output direction of the I / O terminal of the slave device. This operation is sequentially performed on all slave devices on the transmission path. As a result, the direction switching command transmitted by the host is transferred by each ring-shaped slave device, goes around the transmission path, and returns to the host device again.

  (B) The host device recognizes that the transmission direction of the ring-shaped transmission line has been switched because the direction switching command transmitted by itself has returned around the transmission line.

<Transmission direction switching operation of ring transmission path>
FIG. 6 shows, in time series, transmission / reception of a direction switching command of the host device and each slave device, and switching between input (R) and output (T) of two I / O terminals of each device. 6 shows an example in which the host device 1, the slave device 2, the slave device 3,..., And the slave device N are connected in this order. In FIG. 6, the I / O terminals having R and T respectively indicate that the respective I / O terminals are in the R (input) and T (output) states. Hereinafter, the description of R and T to the I / O terminal in each figure is the same.

  (1) The host device 1 transmits a direction switching command 70 from the I / O terminal P12 to the slave device 2. The slave device 2 receives the transmitted direction switching command at the I / O terminal P21.

  (2) The host device 1 switches the I / O terminal P12 from output (T) to input (R).

  (3) The slave device 2 switches the I / O terminal P21 from input (R) to output (T), and transfers a direction switching command from the I / O terminal P22 to the I / O terminal P31 of the slave device 3.

  (4) The slave device 2 switches the I / O terminal P22 from output (T) to input (R).

  (5) Each of the slave devices 3 to N performs the same operation as that of the slave device 2 and transfers a direction switching command.

  (6) The slave device N transfers a direction switching command to the host device 1.

  (7) The host device receives the direction switching command from the I / O terminal P11 and switches the I / O terminal P11 from input (R) to output (T). The host device recognizes that the transmission direction of the ring-shaped transmission line has been switched because the direction switching command transmitted from the I / O terminal P12 has made a round on the transmission line and returns to the I / O terminal P11.

  In the above, each slave device transfers the direction switching command to the next adjacent device if the packet received by itself is a direction switching command, but the host device has a special destination address for the packet described above. By setting the address, each slave device may transfer the direction switching command to the next adjacent device when a special address is set as the destination address of the packet received by itself. For example, it is assumed that the device number is assigned to the address such that the address of the host device 1 is 1, the address of the slave device 2 is 2,..., The address of the slave device N is N. At this time, the host device 1 sets an address other than that assigned to each device, for example, 0 as a special address to 0 as a packet transmission destination, and transmits a direction switching command to the slave device 2. The slave device 2 that has received the direction switching command transfers the direction switching command to the slave device 3 when confirming that 0 is set in the transmission destination address from the analysis result of the packet. Thereafter, each slave device may transfer the direction switching command in the order of slave device 3 → slave device 4 →... → slave device N → host device 1.

  Hereinafter, the input / output switching operation of the I / O terminal in the host device 1 and the slave device m will be described in detail.

<Input / output switching operation 1 of I / O terminal of host device 1>
FIG. 7A shows the state of the host device 1 before issuing the direction switching command. The input / output switching control unit 204 maintains the voltage of the input / output switching control lines 213 and 214 at a high level, the I / O terminal 205 is connected to the input buffer 211, and the I / O terminal 206 is connected to the output buffer 212.

  With reference to FIG. 7A as an initial state, an operation of switching between input and output of the I / O terminals 205 and 206 will be described. FIG. 9A shows a flowchart of the input / output switching operation of the I / O terminal of the host device 1. Hereinafter, the numbers in parentheses indicate step identification numbers in FIG. 9A.

  When the host device 1 switches the input / output of the I / O terminals 205 and 206 (S10), first, the control unit 200 in the host device 1 checks the state determination unit 203. When the state determination unit 203 indicates a state in which input / output switching is possible (S11), the control unit 200 notifies the command generation unit 201 of the direction switching control information. When the state determination unit 203 does not indicate a state where input / output switching is possible, the control unit 200 waits until the state determination unit 203 indicates a state where input / output switching is possible (S11). Then, the control unit notifies the command generation unit 201 of the direction switching control information. Here, the state in which input / output switching is possible means that, for example, the control unit in the host device is in a standby state.

  The command generation unit 201 receives the I / O terminal direction switching control information from the control unit 200, generates a direction switching command, and transmits it from the I / O terminal 206 via the output buffer 212 (S12). Then, the command generation unit 201 notifies the input / output switching control unit 204 of the completion of transmission of the direction switching command. In response to this transmission completion notification, the input / output switching control unit 204 changes the input / output switching control line 214 currently in the low level state from the low level (L) to the high level (H). As a result, as shown in FIG. 9B, the I / O terminal 206 is switched from output to input (S13).

  At this time, the input / output switching control unit 204 stores that the input / output switching of the I / O terminal 206 has been completed.

  The direction switching command transmitted from the host device 1 is sequentially transferred by the slave devices 2 to N of the ring-shaped transmission line system 10. The host apparatus 1 receives the direction switching command that has made a round around the ring-shaped transmission line at the I / O terminal 205 (S14). Then, it is analyzed as a direction switching command by the command analysis unit 202 and the result is notified to the control unit. Upon receiving this notification, the control unit 200 confirms the state determination unit 203. The control unit 200 waits until the state determination unit 203 indicates a state where input / output switching is possible (S15). When the state determination unit 203 is in a state where input / output switching is possible, the control unit notifies the input / output switching control unit 204 of input / output switching control information of the I / O terminal. In response to the input / output switching notification of the I / O terminal from the control unit 200, the input / output switching control unit 204 sets the input / output switching control line 213 of the I / O terminal 205 that has not been switched to the high level ( From H) to low level (L). As a result, as shown in FIG. 9C, the I / O terminal 205 is switched from input to output (S16). The input / output switching control unit 204 notifies the control unit 200 that the input / output switching of the two I / O terminals 205 and 206 has been completed (S17).

<Input / output switching operation 2 of I / O terminal of host device 1>
When the host device 1 switches input / output of the I / O terminals 205 and 206, first, the control unit 200 in the host device 1 checks the state determination unit 203. When the state determination unit 203 indicates a state in which input / output switching is possible, the control unit 200 notifies the command generation unit 201 of direction switching control information. When the state determination unit 203 does not indicate a state where input / output switching is possible, the control unit 200 waits until the state determination unit 203 indicates a state where input / output switching is possible. Then, the control unit notifies the command generation unit 201 of the direction switching control information. The command generation unit 201 receives the I / O terminal direction switching control information from the control unit 200, generates a direction switching command, and transmits it from the I / O terminal 206 via the output buffer 212. The direction switching command transmitted from the host device 1 is sequentially transferred by the slave devices 2 to N of the ring-shaped transmission line system 10. The host device 1 receives the direction switching command that has made a round around the ring-shaped transmission path at the I / O terminal 205. Then, it is analyzed as a direction switching command by the command analysis unit 202 and the result is notified to the control unit 200. Upon receiving this notification, the control unit 200 confirms the state determination unit 203. The control unit 200 waits until the state determination unit 203 indicates a state where input / output switching is possible. When the state determination unit 203 is in a state where input / output switching is possible, the control unit notifies the input / output switching control unit 204 of input / output switching control information of the I / O terminals 205 and 206. The input / output switching control unit 204 receives the input / output switching notification of the I / O terminals 205 and 206 from the control unit 200 and inputs the input / output switching control line 213 from the high level (H) to the low level (L). The output switching control line 214 is changed from the low level (L) to the high level (H). As a result, the I / O terminal 205 is switched from input to output, and the I / O terminal 205 is switched from output to input. The input / output switching control unit 204 notifies the control unit 200 that the input / output switching of the two I / O terminals 205 and 206 has been completed.

<Input / output switching operation 1 of I / O terminal of slave device m>
FIG. 8A shows the state of the slave device m before receiving the direction switching command. The input / output switching control unit 304 maintains the voltage of the input / output switching control lines 313 and 314 at a high level, the I / O terminal 305 is connected to the input buffer 211, and the I / O terminal 306 is connected to the output buffer 212. With reference to FIG. 8A as an initial state, an operation of switching between input and output of the I / O terminals 305 and 306 will be described. FIG. 9B is a flowchart of the input / output switching operation of the I / O terminal of the slave device m. Hereinafter, the numbers in parentheses indicate the step identification numbers in FIG. 9B.

  The slave device m receives the direction switching command transmitted from the host device 1 or transferred from another adjacent slave device at the I / O terminal 305 (S20, S21). The received command is analyzed as a direction switching command by the command analysis unit 302 via the input buffer 311, and the result is notified to the control unit 301. The control unit 301 receives the notification of the direction switching command and confirms the state determination unit 303. When the state determination unit 303 indicates a state in which input / output switching is possible (S22), the control unit 301 notifies the input / output switching control unit 304 of input / output switching control information of the I / O terminal. When the state determination unit 303 does not indicate a state where input / output switching is possible, the control unit 301 waits until the state determination unit 303 indicates a state where input / output switching is possible (S22). When the state determination unit 303 indicates a state in which input / output switching is possible, the control unit 301 notifies the input / output switching control unit 304 of input / output switching control information of the I / O terminal. The input / output switching control unit 304 receives the input / output switching notification of the I / O terminal from the control unit 301 and changes the input / output switching control line 313 that is currently in the high level state from the high level (H) to the low level (L). To do. As a result, as shown in FIG. 8B, the I / O terminal 305 is switched from input to output (S23). At this time, the input / output switching control unit 304 stores that the input / output switching of the I / O terminal 305 has been completed.

  The input / output switching control unit 304 notifies the control unit 301 that the input / output switching of the I / O terminal 305 has been completed. Upon receiving this notification, the control unit 301 notifies the command analysis unit 302 of control information so as to transfer the direction switching command. The command analysis unit 302 transfers the direction switching command from the I / O terminal 306 via the output buffer 312 (S24). The command analysis unit 302 notifies the control unit 301 that the command transfer has been completed. Then, the control unit 301 notifies the input / output switching control unit 304 of the input / output switching control information of the I / O terminal. In response to the input / output switching notification of the I / O terminal from the control unit 301, the input / output switching control unit 304 sets the input / output switching control line 314 of the I / O terminal 306 that has not been switched to the low level (L ) To high level (H). As a result, as shown in FIG. 8C, the I / O terminal 306 is switched from output to input (S25). The input / output switching control unit 304 notifies the control unit 301 that the input / output switching of the I / O terminals 305 and 306 has been completed (S26).

<Input / output switching operation 2 of I / O terminal of slave device m>
The slave device m receives a direction switching command transmitted from the host device 1 or transferred from another adjacent slave device at the I / O terminal 305. The received command is analyzed as a direction switching command by the command analysis unit 302 via the input buffer 311, and the result is notified to the control unit 301. Upon receiving the notification of the direction switching command, the control unit 301 confirms the state determination unit 303. When the state determination unit 303 indicates a state in which input / output switching is possible, the control unit 301 notifies the command analysis unit 302 of control information so as to transfer the direction switching command. When the state determination unit 303 does not indicate a state where input / output switching is possible, the control unit 301 waits until the state determination unit 303 indicates a state where input / output switching is possible. When the state determination unit 303 indicates a state in which input / output switching is possible, the control unit 301 notifies the command analysis unit 302 of control information so as to transfer a direction switching command. The command analysis unit 302 transfers the direction switching command from the I / O terminal 306 via the output buffer 312. The command analysis unit 302 notifies the control unit 301 that the command transfer has been completed. Then, the control unit 301 notifies the input / output switching control unit 304 of input / output switching of the I / O terminals 305 and 306. The input / output switching control unit 304 receives the input / output switching request of the I / O terminals 305 and 306 from the control unit 301 and inputs / outputs the input / output switching control line 314 from the low level (L) to the high level (H). The switching control line 313 is changed from the high level (H) to the low level (L). As a result, the I / O terminal 306 is switched from output to input, and the I / O terminal 305 is switched from input to output. The input / output switching control unit 304 notifies the control unit 301 that the input / output switching of the I / O terminals 305 and 306 has been completed.

  As described above, by switching the transfer direction using a command in the ring-shaped transmission line, the transfer direction can be switched without using any special wiring between the devices. In addition, the host determines that the switching of all terminals has been completed when the command issued by itself returns to itself, and it does not send or receive switching commands or switching completion commands individually between the terminals. Switching is realized. For this reason, transmission / reception of commands required for switching the transfer direction can be minimized, and power consumption for switching the transfer direction can be suppressed.

  By using such a ring-shaped transmission line system 10, it is possible to suppress power consumption associated with data transfer. For example, in the adjacent slave devices 2 and 3, the data transfer direction at a certain point in time is the direction from the slave device 2 to the slave device 3. At this time, when sufficiently large data is transferred from the slave device 3 to the slave device 2, the data transfer direction is switched by the host device 1. As a result, the number of devices through which data is transferred can be minimized, and power consumption associated with data transfer can be suppressed.

  As described above, in the ring-shaped transmission line system according to the present embodiment, switching of the transmission direction of the ring-shaped transmission line can be realized by rotating the direction switching command once in the ring-shaped transmission line. That is, it is possible to easily switch the transmission direction by utilizing an existing ring-shaped transmission path without adding a new control line.

  In addition, the host device 1 includes a state determination unit 203 that determines whether the two input / output terminals can be switched based on the operation status, and the host control unit (control unit 200) includes the state determination unit When the unit 203 determines that switching is possible (S11 in FIG. 9A), the direction switching command is transmitted from the first input / output terminal. According to this configuration, it is possible to reduce the performance degradation of the communication device due to the switching of the transmission direction by determining the operation state of the communication device (for example, the state where the processing load is light or the standby state), and consequently the switching of the transmission direction. Degradation of the transmission performance of the ring-shaped transmission line can be reduced.

  In addition, the host control unit of the host device 1 receives the direction switching command that makes one round of the ring-shaped transmission line from the second input / output terminal, and the state determination unit 203 is switchable. When it is determined (S15), the two input / output terminals are controlled so as to reverse the transmission direction between the two input / output terminals and the ring-shaped transmission line. According to this configuration, it is possible to reduce the performance degradation of the communication device due to the switching of the transmission direction by determining the operation state of the communication device (for example, the state where the processing load is light or the standby state), and consequently the switching of the transmission direction. Degradation of the transmission performance of the ring-shaped transmission line can be reduced.

  Although the data transfer between the adjacent slave devices 2 and 3 is performed here, the number of relay devices is minimized between any slave device and the host device, not limited to the transfer between adjacent slave devices. By controlling the transfer direction in this way, it becomes possible to suppress power consumption.

  Note that the host device may be any communication device connected to the ring-shaped transmission path. Alternatively, the host device may be selected dynamically.

  In addition, step S13 of FIG. 9A may be any timing as long as it is after step S12, and may be simultaneous with step S16.

  In addition, step S23 of FIG. 9B may be any timing as long as it is after step S21 or S22, and may be simultaneous with step S25.

(Second Embodiment)
In the present embodiment, in addition to the function of the first embodiment, the host device can determine whether transfer direction switching has succeeded or not, and when the transfer direction switching has failed, which slave device has failed. A ring-shaped transmission line system that makes it possible to specify whether or not will be described.

  FIG. 10 shows a second embodiment of the present invention. In the ring transmission line system according to the present invention in the second embodiment, in addition to the ring transmission line system shown in the first embodiment, the host device 1 has a timer unit β11 and slave devices 2 to N. The switching completion / failure notification generation unit β13 and the timer unit β14 are provided.

  The configurations of the host device 1 and the slave devices 2 to N in the second embodiment are shown in FIGS. Details of each device will be described later.

  The timer units (β11, β14) of the respective devices are set to the first initial values T11 to T1n or the second initial values according to the respective devices and operation states by the respective control units (301, 302), and are constant. If the timer has a countdown timer function that counts down every period and the timer value indicates 0, the timer unit notifies the control unit of the occurrence of a timeout.

  Next, the transfer direction switching operation of the ring transmission line system 10 in the second embodiment will be described.

  FIG. 11 shows, in chronological order, operations when transmission / reception of the direction switching command of the host device and the slave device and switching between input (R) and output (T) of the I / O terminal are normally performed. . Details of the operation of each device will be described later.

  Time (10): The host device 1 transmits a direction switching command 70 from the I / O terminal P12.

  At this time, the host device 1 sets an initial value T12 in the timer unit β11 and starts counting down.

  The slave device 2 receives the transmitted direction switching command at the I / O terminal.

  Time (11): The host device 1 switches the I / O terminal P12 from output (T) to input (R).

  Time (12): Slave device L-1 (L is a natural number of 3 ≦ L ≦ N) receives the direction switching command 70 from the I / O terminal PL01.

  Time (13): Slave device L-1 switches I / O terminal PL01 from input (R) to output (T), and transfers direction switching command 70 from I / O terminal PL02.

  At this time, the slave device L-1 sets an initial value T (L-1) 1 in the timer unit β14 and starts counting down.

  Time (14): Slave device L-1 switches I / O terminal PL02 from output (T) to input (R), and from I / O terminal PL01 to slave device L-2 (when L> 3) or A switching completion notification β12 is transmitted with the host device 1 (in the case of L = 3) as the destination.

  When the slave device L-2 (in the case of L> 3) or the host device 1 (in the case of L = 3) receives the transmitted switching completion notification β12, the slave device L-2 stops the countdown of its own timer units β11 and β14.

  Thereafter, each of the slave devices L to N performs the same operation as that of the slave device L-1, and switches the input / output of the I / O terminal to the slave device connected in the data transfer direction before the direction change. The switching command is transferred, and a switching completion notification is transmitted to the slave device connected in the data transfer direction after the direction switching.

  Time (15): The slave device N performs the same operation as that of the slave device L-1, and transfers the direction switching command 70 to the host device 1.

  Time (16): The slave device N transmits a switch completion notification β12 to the slave device N-1.

  The slave device N-1 that has received the switching completion notification β12 stops the countdown of its own timer unit β14.

  Time (17): The host device 1 that has received the direction switching command 70 at time 15 switches the I / O terminal P11 from input (R) to output (T).

  By operating as described above, the host apparatus 1 recognizes that the transmission direction of the ring-shaped transmission line system 10 has been switched because the direction switching command 70 transmitted by itself has returned around the transmission line. .

  In FIG. 11, the direction switching of the I / O terminal PL11 of the slave device L that has already received the direction switching command at time 13 is performed at the time of transmission of the switching completion notification β12 from the slave device L-1 (time 14). Although not shown, the direction switching of the I / O terminal PL11 may be performed simultaneously with the transmission of the switching completion notification, and is performed before the transmission of the switching completion notification β12 from the slave device L-1. It doesn't matter.

  On the other hand, FIG. 12 shows the operation when the slave device L + 1 cannot switch the direction in time series.

  From time (20) to time (23), each device performs the same operation as when the switching is normally performed, and the direction switching command 70 transmitted from the host device 1 is sent to each slave device 2 -L. Sequential transfer with -1 direction switching.

  Time (22): The direction switching command 70 is transferred from the slave device L to the slave device L + 1.

  Time (23): The switch completion notification β12 is transmitted from the slave device L to the slave device L-1.

  Time (24): When the direction switching is not performed in the slave device L + 1, the slave device L does not receive the direction switching completion notification from the slave device L + 1.

  Time (25): When the timer unit of the slave device L indicates 0 as a result of the countdown, the slave device L switches the I / O terminal PL12 from input (R) to output (T).

  Time (26): The slave device L transmits the direction switching failure notification β15 from the I / O terminal PL11, with itself as the transmission source and the host device 1 as the transmission destination.

  Slave device L-1 receives direction switching failure notification β15 from slave device L at I / O terminal PL02.

  Time (27): Slave device L switches I / O terminal PL11 from output (T) to input (R).

  Time (28): Slave device L-1 switches I / O terminal PL02 from input (R) to output (T).

  Time (29): The slave device L-1 transfers the direction switching failure notification β15 from the I / O terminal PL01.

  Time (2A): Slave device L-1 switches I / O terminal PL01 from output (T) to input (R).

  Thereafter, the same operation as that of the slave device L-1 is repeated in each of the slave devices 2 to L-2.

  Time (2B): The host device 1 receives the direction switching failure notification β15 from the I / O terminal P12.

  Time (2C): Since the host device 1 switches the I / O terminal P12 from the input (R) to the output (T) and the transmission source of the direction switching failure notification β15 is the slave device L, the slave device L + Recognize that the direction change in 1 failed.

Next, FIG. 13 shows a configuration of the host device 1 in the second embodiment.
The host device 1 in the second embodiment is assumed to include a timer unit β11 in the host device shown in FIG. 4 in the first embodiment.

FIG. 15 shows an operation flowchart of the host apparatus 1 regarding the direction switching.
Here, before the direction change, the I / O terminal P11 of the host device 1 is input (R) and the I / O terminal P12 is output (T), similarly to the time 20 in FIG. 12 and the time 20 in FIG. The I / O terminal PN2 of the slave device N that is output (T) after being connected to the slave devices 2, 3,... N in order of the data transmission direction from the host device at the time is the host device. 1 is connected to the I / O terminal P11.

  In performing the direction switching, the host device 1 inquires of the state determination unit 203 whether or not it can switch the direction (Sβ501).

  If it is determined that switching is possible, the control unit 200 of the host device 1 instructs the command generation unit 201 to transmit the direction switching command 70 from the output buffer 212 via the I / O terminal P12 (Sβ502).

  Next, the control unit 200 sets an initial value T12 in the timer unit β11 (Sβ503), and starts a countdown timer (Sβ504).

  The control unit 200 instructs the input / output switching control unit 204 to switch the input / output of the I / O terminal P12 (206), thereby switching the I / O terminal P12 (206) from output (T) to input (R). (Sβ505).

  The host device 1 waits for a notification from the slave device until the timer value T of the timer unit β11 becomes 0 and a timeout occurs (Sβ506). At this time, if there is no notification before the timeout occurs, the host device 1 assumes that the slave device 2 has failed in the direction switching, stops the timer (Sβ508), and inputs the I / O terminal P12 (R). Is switched to output (T) (Sβ509), and the direction switching process is terminated (Sβ510).

  On the other hand, if the notification is received before the timeout occurs, the host device 1 stops the timer (Sβ511) and waits for reception of a command or notification (Sβ513).

  When the host device 1 receives a command or notification from the I / O terminal P11 or P12, the command analysis unit 202 analyzes the command / notification (Sβ514). If the received data is a direction switching failure notification, the location of the switching is specified by specifying the notification transmission source, and the control unit 200 and the input / output switching control unit 204 are assumed to have failed the direction switching. As a result, the I / O terminal P12 is switched from input (R) to output (T), and the direction switching process ends.

  If the received data is a direction switching command, the timer of the timer unit β11 is set to the initial value T11 and the countdown timer is started.

  If the state determination unit 203 does not determine that the direction can be changed before the timer value T of the countdown timer reaches 0 and a timeout occurs, the host device 1 stops the timer (Sβ519) and enters a command / notification reception waiting state. Become. In this case, in the slave device N, a direction switching failure notification is transmitted, received by the host device 1 via the slave devices N-1... 2 and input to the I / O terminal P12 as the direction switching failure. Switching from (R) to output (T) (Sβ509), the direction switching process ends (Sβ510).

  On the other hand, if it is determined that the direction can be switched before the timeout occurs, the timer of the timer unit β11 is stopped, and the input / output switching control unit 204 outputs the I / O terminal P11 from the input (R) to the output (T). (Sβ521). Thereafter, a switch completion notification is transmitted from the I / O terminal P11 to the slave device N (Sβ522). When the slave device N receives the switching completion notification, the direction switching process of the ring transmission line system 10 is completed.

The above is the operation of the host device 1 in the transmission direction switching process.
Next, FIG. 14 shows the configuration of the slave device 2 in the second embodiment.

  The slave device 2 in the second embodiment is assumed to include the timer unit β14 and the switching completion / failure notification generation unit β13 in the slave device shown in FIG. 5 in the first embodiment.

  FIG. 16 shows an operation flow of the slave device M (M is a natural number of 1 ≦ M ≦ N) related to the direction switching. Assume that the I / O terminal PM1 is input (R) and PM2 is output (T) at the start of operation.

  When the slave device M receives the command or notification, the command analyzing unit 302 analyzes the contents (Sβ602). If the direction switching command is received, the timer initial value Tm1 is set in the timer of the timer unit β14, and the countdown timer is started (Sβ603, Sβ604).

  If the state determination unit 303 does not determine that the direction can be switched before the timeout occurs, the slave device M ends the direction switching process (Sβ607).

  When it is determined that the direction can be switched before the timeout occurs, the timer of the timer unit β143 is stopped and the I / O terminal PM1 is switched from the input (R) to the output (T) (Sβ610). Subsequently, the direction switching command 70 is transferred from the I / O terminal PM2 to the slave device M + 1 (the host device 1 when M = N) by the control unit 301, the command analysis unit 302, and the output buffer 312.

  Further, the timer initial value Tm2 is set in the timer of the timer unit β14 of the control unit 301, and the countdown timer is started (Sβ612, Sβ613).

  Thereafter, the control unit 301 and the input / output switching control unit 304 switch the I / O terminal PM2 from output (T) to input (R) (Sβ614), and the switching completion / failure notification generating unit β13 issues a switching completion notification. The data is transmitted from the I / O terminal PM1 to the slave device M-1 (the host device 1 when M = 1) through the output buffer.

Thereafter, the slave device M waits for a notification from the slave device M + 1.
If there is no notification from the slave device M + 1 before the countdown timer of the timer unit β14 becomes 0 and a timeout occurs, the slave device M stops the timer (Sβ618), and the slave device M + 1 fails to switch the direction. As a result, the I / O terminal PM2 is switched from the input (R) to the output (T), and the switching completion / failure notification generating unit β13 issues a switching failure notification with the transmission source and the host as the transmission destination. / O terminal Transmits from PM1. After transmission, the I / O terminal PM1 is switched from output (T) to input (R) (Sβ621), and the direction switching process is terminated (Sβ622).

  When the notification from the slave device M + 1 is received before the timeout occurs, the timer is stopped (Sβ624), and the notification received by the command analysis unit 302 is analyzed. If the received notification is a direction switching completion notification, the direction switching process is terminated (Sβ622).

  After the direction switching, when the notification received by the slave device M is analyzed by the command analysis unit 302 (Sβ602), if the direction switching failure notification is received, the slave device M receives the direction switching failure notification by the input / output switching control unit. The switched I / O terminal PM2 is switched from input (R) to output (T) (Sβ626). Thereafter, the received switching failure notification is transferred from the I / O terminal PM1 (Sβ627), the I / O terminal PM1 is switched from output (T) to input (R), and the transfer direction switching process is terminated.

The above is the operation of the slave device M in the transmission direction switching process.
The slave devices 3 to N have the same configuration as that of the slave device 2.

  However, the IO device or memory provided in each slave device may be different.

  In the ring transmission line system 10, when data is transferred from one slave device θ to another slave device π, the data is sufficiently large, and the data is in a direction opposite to the data transfer direction of the current ring transmission line. When it is determined that the number of slave devices and host devices that are transmitted via communication between both slaves is smaller, the data transfer direction is switched using the above-described direction switching command. By switching the direction, it is possible to reduce the number of devices through which data is directly transferred between both slaves, thereby reducing power consumption compared to the case where the transfer direction is not switched.

  As described above, in the host device according to the present embodiment, after the control unit 200 (host control unit) transmits the direction switching command from the first host I / O terminal to the ring transmission line. The first host I / O terminal is switched from output to input (Sβ505), and a switching completion notification indicating that the switching of the transmission direction has been completed from the adjacent slave device on the ring-shaped transmission path is the direction switching command. (Sβ 506, Sβ 507) and whether the switch completion notification is received within the first predetermined time is determined whether it is received from the first host I / O terminal within the first predetermined time (T12) from the transmission of If it is determined that it has not been received, it is determined that switching of the transmission direction has failed, the first host I / O terminal is returned from input to output (Sβ509), and the first host I / O terminal is returned within the first predetermined time. If the completion notification is determined to have been received, wherein the direction switching command from the second host I / O pin is configured to waiting to be received (Sβ513).

  The slave device 2 includes a notification generation unit (β13) that generates a switching completion notification indicating completion of switching between output and input of the two slave I / O terminals according to the direction switching command, and the slave control unit (Control unit 301) further transmits a switching completion notification generated by the notification generation unit from the first slave I / O terminal after completion of switching between the input and output of each of the two slave I / O terminals. (Sβ615).

  According to this, since the slave device transmits a switching completion notification to the host device that is the source of the direction switching command, the host device can easily determine whether or not the transmission direction switching is successful.

  In addition, the host control unit further causes the slave device on the ring-shaped transmission path to fail to switch the transmission direction after transmitting the direction switching command from the first host I / O terminal to the ring-shaped transmission path. It is determined whether or not a switching failure notification indicating that the transmission direction has been received from the first host I / O terminal (Sβ514). If the switching failure notification is received, it is determined that switching of the transmission direction has failed. The one of the two host I / O terminals is returned from the input to the output (Sβ509).

  The slave control unit indicates that the switching of the transmission direction has been completed in the adjacent host device within the second predetermined time (Tm2) from the transmission of the direction switching command from the second slave I / O terminal. It is determined whether or not a switching completion notification has been received from the second slave I / O terminal (Sβ616 + Sβ617), and the notification generation unit has not received a switching completion notification within the second predetermined time. The slave control unit generates a switching failure notification indicating that the adjacent slave device has failed to switch the transmission direction, and the slave control unit further displays the switching failure notification generated by the notification generating unit. 1 from the slave I / O terminal (Sβ620), and the input and output of each of the two slave I / O terminals are returned to the same state as before receiving the direction switching command (S β619 + Sβ621).

  According to this, since the switching failure notification is transmitted from the slave device adjacent to the slave device that has failed to be switched, the host device can easily detect the success or failure of switching of the transmission direction.

  Further, the notification generation unit in the slave device 2 generates the switching failure notification including the address of its own slave device, and the host control unit further receives the switching failure when the switching failure notification is received. The slave device that failed to switch the transmission direction is identified based on the notification source address (Sβ523).

  According to this, it is possible to easily identify the slave device that has failed to switch the transmission direction, for example, it is possible to identify the failed host device.

  Further, the slave control unit determines whether or not a switching failure notification indicating that the switching of the transmission direction has failed in any slave device on the ring-shaped transmission path is received from the second slave I / O terminal. If it is determined (Sβ602) and it is determined that the switching failure notification is received from the second slave I / O terminal, the switching failure notification is transmitted from the first slave I / O terminal (Sβ620), The two slave I / O terminals are configured to return to the same state as before receiving the direction switching command (Sβ619 + Sβ621).

  According to this, since the switching failure notification is sequentially transferred by a plurality of slave devices on the ring-shaped transmission path, for example, a failed slave device can be easily identified.

  In the above, the transmission timing of the switching completion notification β12 from the slave device is after the transmission of the direction switching command 70 to the next slave, but the switching completion notification β12 and the direction switching command 70 may be transmitted simultaneously. I do not care.

  In the above, the transmission timing when each device transfers the direction switching failure notification β15 is after the direction switching of the I / O terminal that received the direction switching failure notification β15, but at the same time as the direction switching or before the direction switching. It does not matter.

  In the above description, the operation of each timer unit is a countdown timer. However, the timer is a countup timer, and the elapsed time is measured by comparing the timer values with predetermined values T11 to TN1, T21 to T2N. May be notified from the timer units β11 and β14 to the control units 200 and 301.

  In this embodiment, the direction switching failure notification β15 is sent from the slave device L to the host device 1, but the destination of the direction switching failure notification transmitted by the slave device L may be the slave device L-1. Absent. In this case, each slave device repeats the direction switching failure notification β15 to the adjacent slave device or host device, for example, the slave device L-1 transmits a direction switching failure notification addressed to the slave device L-2. Accordingly, the host device 1 is notified of the direction switching failure notification β15. At this time, the address of the failure occurrence device may be included in the direction switching notification β15 so that the host device 1 can identify the location where the failure has occurred.

  In the present embodiment, the direction switching failure notification and the direction switching completion notification transmitted by the slave device are used, but these notifications may be commands.

  In this embodiment, the data can be directly transferred between the slaves, but the data can be transferred only between the host and the slave. In this case, transfer between desired devices can be realized by switching the host and slave.

  In the present embodiment, one host device exists in one ring-shaped transmission line, but there may be a plurality of other host devices.

  As described above, according to the second embodiment of the present invention, when the host device and each slave device operate, the direction switching with the reduced command transmission amount is realized and the direction switching fails. The host device can identify the device that failed to be switched. Further, at this time, the input / output direction of the I / O terminal of each device can be returned to the state before switching the transfer direction, and the original state can be recovered.

  Also, according to the second embodiment, when a slave device fails and data transmission / reception or direction switching cannot be performed, the failure slave device can be identified by using a direction switching command. I can do it.

  Note that step Sβ619 in FIG. 16 may be after step Sβ610 or at the same time as step Sβ621.

  Further, step Sβ626 in FIG. 16 may be after step Sβ627 or may be performed simultaneously with step Sβ628.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

  FIG. 17 is a block diagram of a ring-shaped transmission line system showing a third embodiment of the present invention. In FIG. 17, α1 is one host device, α2 to αN are a plurality of slave devices operating under the control of the host device α1, α10 is a transmission path, and the above is the same as the configuration of FIG. 2 is different from the configuration of FIG. 2 in that the timer unit α11 is set to the host device α1 to start counting from the time when the direction switching command α70 is transmitted to the adjacent slave device α2 (αN when operating in the clockwise direction). Provided, and the host device α1 transmits a switching completion notification generation unit α13 that returns a switching completion notification α12 to the host device α1 to a plurality of slave devices α2 to αN that operate under the control of the host device α1, or other adjacent devices In response to the direction switching command transferred from the slave devices α3 to N, the I / O terminal input / output switching operation is completed and returned.

  Configurations of the host device α1 and the slave devices α2 to αN in the third embodiment are shown in FIGS. Details of each device will be described later.

  FIG. 18 is a configuration diagram of the host device α1 in the third embodiment, which is different from the configuration in FIG. 4 in that a timer unit α215 is provided to start counting from the time point when the direction switching command α70 is transmitted in the control unit 200. Is a point.

  The timer unit α215 of the host device α1 is set to an initial value T0 by the control unit 200, and has a countdown timer function that counts down at regular intervals. Will be notified. The control unit shifts the state determination unit 203 to a state in which input / output switching cannot be performed by a notification of timeout, stops the system, and analyzes the source address in the notification of switching completion immediately before the timeout received from the command analysis unit 202 To identify the fault location.

  FIG. 19 is a configuration diagram of the slave devices α2 to αN in the third embodiment, which is different from the configuration in FIG. 5 in that a signal indicating that the input / output switching operation of the I / O terminal has been completed in response to the direction switching command In other words, a switching completion notification generation unit α315 that issues a switching completion notification is provided.

  Next, the transfer direction switching operation of the ring transmission line system 10 in the third embodiment will be described.

  FIG. 20 shows, in time series, operations when transmission / reception of the direction switching command between the host device and the slave device and switching between input (R) and output (T) of the I / O terminal are normally performed. Details of the operation of each device will be described later.

  Time (50): The host device 1 transmits a direction switching command 70 from the I / O terminal P12.

  At this time, the host device 1 sets an initial value T0 in the timer unit α11 and starts counting down.

  The slave device 2 receives the transmitted direction switching command 70 at the I / O terminal.

  Time (51): The host device 1 switches the I / O terminal P12 from output (T) to input (R).

  Time (52): Slave device L-1 (L is a natural number of 3 ≦ L ≦ N) receives the direction switching command 70 from the I / O terminal PL01.

  Time (53): Slave device L-1 switches I / O terminal PL01 from input (R) to output (T), and transfers direction switching command 70 from I / O terminal PL02.

  Time (54): The slave device L-1 switches the I / O terminal PL02 from output (T) to input (R), and transmits a switch completion notification β12 from the I / O terminal PL01 to the host device 1 as the destination. To do.

  Thereafter, each of the slave devices L to N performs the same operation as that of the slave device L-1, and switches the input / output of the I / O terminal to the slave device connected in the data transfer direction before the direction change. The switching command is transferred, and a switching completion notification is transmitted with the host device 1 as the destination in the data transfer direction after the direction switching.

  Time (55): The slave device N performs the same operation as that of the slave device L-1, and transfers the direction switching command 70 to the host device 1.

  Time (56): The slave device N transmits the switching completion notification β12 with the host device 1 as the destination.

  Time (57): The host device 1 that has received the direction switching command 70 at time (55) switches the I / O terminal P11 from input (R) to output (T).

  The host device 1 stops the countdown of the timer unit α215 when the direction switch command 70 issued by the host device 1 receives the switch completion notification β12 transmitted from the slave device N after returning around the transmission path. .

  In FIG. 20, the direction switching of the I / O terminal PL11 of the slave device L that has already received the direction switching command at time 53 is performed at the transmission time (time (54)) of the switching completion notification β12 from the slave device L-1. Although not performed, it may be simultaneously with the transmission of the switching completion notification, and the direction switching of the I / O terminal PL12 is performed prior to the transmission of the switching completion notification β12 from the slave device L-1. It doesn't matter.

  On the other hand, FIG. 21 shows an operation in a time series when the slave device L + 1 cannot change the direction.

  From time (60) to time (63), each device performs the same operation as when switching is performed normally, and the direction switching command 70 transmitted from the host device 1 is sent to each slave device 2−L−. It is transferred with the direction change of 1.

  Time (62): The direction switching command 70 is transferred from the slave device L to the slave device L + 1.

  Time (63): The switching completion notification β12 is transmitted from the slave device L to the host device 1.

  Time (64): When the direction switching is not performed in the slave device L + 1, the host device 1 does not receive the direction switching completion notification from the slave device L + 1.

  Time (65) to Time (67): Thereafter, when the host device 1 cannot receive the switching completion notification β12 from the slave device L + 1 and the timer value indicates the countdown result 0, the timer unit The control unit is notified of the occurrence of timeout. The control unit shifts the state determination unit 203 to a state where input / output switching is not possible in response to a timeout notification, and stops the system.

  The host device 1 receives the notification of the completion of switching from the slave device 2 to the slave device L at the time of timeout, and determines that the slave device L + 1 has failed in the direction switching because it has not received the notification of the completion of switching of the slave device L + 1.

The slave devices 3 to N have the same configuration as that of the slave device 2.
However, the IO device or memory provided in each slave device may be different.

  In the above, the transmission timing of the switching completion notification from the slave device is after the transmission of the direction switching command, but the direction switching completion notification and the transmission of the direction switching command may be simultaneous.

  In the above description, the operation of each timer unit is a countdown timer. However, the countdown timer is used, and the time elapses by comparing the timer value with a predetermined value (for example, the arrival time in which the direction switching command is made once). The timer unit may notify the control unit when a predetermined time has elapsed.

  As described above, according to the third embodiment, when a specific slave device fails and data transmission / reception or direction switching cannot be performed, a failed slave device is used by using a direction switching completion notification. Can be detected.

  The ring-shaped transmission line system according to the present invention realizes switching of the transfer direction without using a special wiring between devices, and further enables switching of the transmission direction while minimizing the transmission / reception of commands, thereby reducing power consumption. Since it has a feature that it can be suppressed, it is useful for realizing a device requiring low power consumption technology such as an audio visual device or a mobile device.

1 Host device 2 to N Slave device 10 Ring transmission line system 11 LSI
12 CPU
13 bus 14 I / O terminal 41 data type 42 transmission source address 43 transmission destination address 44 data 200 control unit 201 command generation unit 202 command analysis unit 203 state determination unit 204 input / output switching control unit 205, 206 I / O terminals 207 to 210 Direction switching buffer 211 Input buffer 212 Output buffer 213, 214 Input / output switching control line 300 Memory or IO device 301 Control unit 302 Command analysis unit 303 Status determination unit 304 Input / output switching control unit 305, 306 I / O terminals 307 to 310 Direction switching buffer 311 Input buffer 312 Output buffer 313, 314 Input / output switching control line 70 Direction switching command
P11, P12, P21, P22,..., PN1, PN2 I / O terminals β11, β14 Timer unit β12 Switching completion notification β13 Switching completion / failure notification generating unit α11, α215 Timer unit α12 Switching completion notification α13, α315 Switching completion Notification generator α70 Direction switch command

Claims (20)

A communication device connected to a ring-shaped transmission line,
Two input / output terminals connected to the ring-shaped transmission line and capable of switching between input and output;
A command generation unit that generates a direction switching command that instructs all other communication devices to switch the transmission direction of the ring-shaped transmission path;
A control unit for controlling the two input / output terminals and the command generation unit,
The controller is
The direction switching command is transmitted from the first input / output terminal which is one of the two input / output terminals to the ring-shaped transmission line,
The two input / output terminals and the ring-shaped transmission path when the direction switching command that makes one round of the ring-shaped transmission path is received from a second input / output terminal that is the other of the two input / output terminals. A communication device that controls switching of the two input / output terminals so as to invert the transmission direction between the two and the direction before the transmission of the direction switching command. The communication device further includes a state determination unit that determines whether the two input / output terminals can be switched based on an operation state of the communication device,
The communication device according to claim 1, wherein the control unit transmits the direction switching command from the first input / output terminal when the state determination unit determines that the switching is possible. The communication device further includes a state determination unit that determines whether the two input / output terminals can be switched based on an operation state of the communication device,
The control unit, when the direction switching command that makes one round of the ring-shaped transmission path is received from the second input / output terminal, and the state determination unit determines that the two can be switched, The communication apparatus according to claim 1, wherein the two input / output terminals are controlled so as to reverse a transmission direction between the input / output terminals and the ring-shaped transmission line. The control unit further includes:
After the direction switching command is transmitted from the first input / output terminal to the ring-shaped transmission line, the first input / output terminal is switched from output to input,
Whether a switching completion notification indicating that the switching of the transmission direction has been completed is received from the first input / output terminal within a first predetermined time from the transmission of the direction switching command from the adjacent communication device on the ring-shaped transmission path. Determine whether or not
If it is determined that the switch completion notification has not been received within the first predetermined time, it is determined that transmission direction switching has failed, and the first input / output terminal is returned from input to output,
2. The communication device according to claim 1, wherein when it is determined that the completion notification is received within the first predetermined time, the communication apparatus waits for the direction switching command to be received from the second input / output terminal. The control unit further includes:
After transmitting the direction switching command from the first input / output terminal to the ring-shaped transmission path, a switching failure notification indicating that switching of the transmission direction has failed in any communication device on the ring-shaped transmission path, Determining whether it is received from the first input / output terminal;
The communication apparatus according to claim 4, wherein when the switching failure notification is received, it is determined that the switching of the transmission direction has failed, and the one of the two input / output terminals is returned from the input to the output. The control unit further includes:
The communication device according to claim 5, wherein when the switch failure notification is received, the communication device that has failed to switch the transmission direction based on a transmission source address of the switch failure notification. The said control part switches the said 2nd input / output terminal from an input to an output, when the said direction switch command which went round the said ring-shaped transmission line is received from the said 2nd input / output terminal. The communication apparatus in any one of. A communication device connected to a ring-shaped transmission line,
Two input / output terminals connected to the ring-shaped transmission line and capable of switching between input and output;
By analyzing a command received from the first input / output terminal which is one of the two input / output terminals, the command is a direction switching command for instructing switching of the transmission direction of the ring-shaped transmission path. A command analysis unit for determining whether or not
When it is determined that the command received from the first input / output terminal is the direction switching command, the direction switching command is transmitted from the second input / output terminal which is the other of the two input / output terminals, A communication apparatus comprising a control unit that switches between input and output of each of the two input / output terminals. The communication device further includes:
A state determination unit that determines whether the two input / output terminals can be switched based on an operation state of the communication device;
The controller is
If it is determined that the command received from the first input / output terminal is the direction switching command and the state determination unit determines that switching is not possible, the determination of the state determination unit changes. Wait,
9. The communication apparatus according to claim 8, wherein the direction switching command is transmitted from the second input / output terminal and the input and output of each of the two input / output terminals are switched after the determination changes so as to be switchable within a predetermined time. The communication apparatus further includes a notification generation unit that generates a switching completion notification indicating that switching between output and input of the two input / output terminals is completed according to the direction switching command,
9. The control unit according to claim 8, further comprising: after completion of switching between input and output of each of the two input / output terminals, further transmitting a switching completion notification generated by the notification generation unit from the first input / output terminal. Communication device. The controller is
A switch completion notification indicating that the switching of the transmission direction has been completed in the adjacent communication device within the second predetermined time from the transmission of the direction switch command from the second input / output terminal is the second input / output terminal. To determine if it was received from
The notification generation unit further generates a switching failure notification indicating that the adjacent communication device has failed to switch the transmission direction when it is determined that the switching completion notification is not received within the second predetermined time,
The control unit further includes:
The switching failure notification generated by the notification generation unit is transmitted from the first input / output terminal,
The communication apparatus according to claim 10, wherein the input and output of each of the two input / output terminals are returned to the same state as before receiving the direction switching command. The communication device according to claim 11, wherein the notification generation unit generates the switching failure notification including an address of the communication device. The controller is
Determining whether a switching failure notification indicating that switching of the transmission direction has failed in any communication device on the ring-shaped transmission path is received from the second input / output terminal;
When it is determined that the switching failure notification is received from the second input / output terminal, the switching failure notification is transmitted from the first input / output terminal;
The communication apparatus according to claim 11, wherein the two input / output terminals are returned to the same state as before receiving the direction switching command. A ring-shaped transmission line system comprising a host device connected to a ring-shaped transmission line and a plurality of slave devices,
The host device is
Two host I / O terminals connected to the ring-shaped transmission line and capable of switching between input and output;
A command generator for generating a direction switching command for instructing all other slave devices to switch the transmission direction of the ring-shaped transmission path;
A host controller that controls the two host I / O terminals and the command generator,
The host control unit
Sending the direction switching command from the first host I / O terminal, which is one of the two host I / O terminals, to the ring-shaped transmission line;
The two host I / O terminals when the direction switching command that makes one round of the ring-shaped transmission line is received from a second host I / O terminal that is the other of the two host I / O terminals. And control the switching of the two host I / O terminals so as to reverse the transmission direction between the transmission line and the ring-shaped transmission line compared to before transmission of the direction switching command,
Each slave device
Two slave I / O terminals connected to the ring-shaped transmission line and capable of switching between input and output;
A direction in which the command instructs switching of the transmission direction of the ring-shaped transmission line by analyzing a command received from the first slave I / O terminal which is one of the two slave I / O terminals. A command analysis unit for determining whether the command is a switching command;
When it is determined that the command received from the first slave I / O terminal is the direction switching command, the direction switching command is sent to the second slave I / O that is the other of the two slave I / O terminals. A ring transmission line system comprising a slave control unit that transmits from the O terminal and switches between input and output of each of the two slave I / O terminals. The host device further includes a host state determination unit that determines whether the two host I / O terminals can be switched based on an operation state of the host device,
The host control unit transmits the direction switching command from the first host I / O terminal when the host state determination unit determines that the switching is possible,
Each slave device further comprises:
A slave state determination unit that determines whether the two slave I / O terminals can be switched based on an operation state of the slave device;
The slave control unit
When it is determined that the command received from the first slave I / O terminal is the direction switching command and the slave state determination unit determines that switching is not possible, the determination of the slave state determination unit changes. Wait for
15. The direction switching command is transmitted from the second slave I / O terminal after the determination is changed so as to be switchable within a predetermined time, and the input and output of each of the two slave I / O terminals are switched. Ring transmission line system. The host control unit further includes:
After the direction switching command is transmitted from the first host I / O terminal to the ring transmission line, the first host I / O terminal is switched from output to input,
A switching completion notification indicating that transmission direction switching has been completed from an adjacent slave device on the ring-shaped transmission line is received from the first host I / O terminal within a first predetermined time from transmission of the direction switching command. Determine if it was received,
If it is determined that the switching completion notification has not been received within the first predetermined time, it is determined that transmission direction switching has failed, and the first host I / O terminal is returned from input to output. ,
If it is determined that the completion notification is received within the first predetermined time, wait for the direction switching command to be received from the second host I / O terminal;
The slave device further includes a notification generation unit that generates a switching completion notification indicating completion of switching between output and input of the two slave I / O terminals according to the direction switching command.
The slave control unit causes the first slave I / O terminal to transmit the switching completion notification generated by the notification generation unit after the switching of the input and output of each of the two slave I / O terminals is completed. The ring-shaped transmission line system according to claim 14. The host control unit further includes:
After transmitting the direction switching command from the first host I / O terminal to the ring-shaped transmission path, a switching failure notification indicating that the switching of the transmission direction has failed in the slave device on the ring-shaped transmission path, Determine whether it is received from the first host I / O terminal,
When the switching failure notification is received, it is determined that the transmission direction switching has failed, and the one of the two host I / O terminals is returned from the input to the output,
The slave control unit
Within the second predetermined time from the transmission of the direction switching command from the second slave I / O terminal, a switching completion notification indicating that switching of the transmission direction has been completed in the adjacent host device is sent to the second slave Determine whether it was received from the I / O terminal,
The notification generation unit further generates a switching failure notification indicating that the adjacent slave device has failed to switch the transmission direction when it is determined that the switching completion notification has not been received within the second predetermined time. And
The slave control unit further includes:
The switching failure notification generated by the notification generation unit is transmitted from the first slave I / O terminal,
17. The ring transmission line system according to claim 16, wherein the input and output of each of the two slave I / O terminals are returned to the same state as before receiving the direction switching command. The notification generation unit generates the switching failure notification including the address of its own slave device,
The ring-shaped transmission line according to claim 17, wherein, when the switch failure notification is received, the host control unit further identifies a slave device that has failed to switch the transmission direction based on a transmission source address of the switch failure notification. system. The slave control unit
Determining whether or not a switching failure notification indicating that switching of the transmission direction has failed in any of the slave devices on the ring-shaped transmission path is received from the second slave I / O terminal;
When it is determined that the switching failure notification is received from the second slave I / O terminal, the switching failure notification is transmitted from the first slave I / O terminal;
18. The ring transmission line system according to claim 17, wherein the two slave I / O terminals are returned to the same state as before receiving the direction switching command. A transmission direction switching method for a ring-shaped transmission line comprising a host device connected to the ring-shaped transmission line and a plurality of slave devices,
The host device includes two host I / O terminals connected to the ring-shaped transmission line and capable of switching between input and output;
Each slave device includes two slave I / O terminals that are connected to the ring-shaped transmission line and can be switched between input and output,
The transmission direction switching method is:
In the host device, generate a direction switching command that instructs all other slave devices to switch the transmission direction of the ring-shaped transmission path,
In the host device, the direction switching command is transmitted from the first host I / O terminal, which is one of the two host I / O terminals, to the ring-shaped transmission line,
In the host device, the direction switching command that has made one round of the ring-shaped transmission line is received from a second host I / O terminal that is the other of the two host I / O terminals,
In the host device, when the direction switching command is received, the transmission direction between the two host I / O terminals and the ring-shaped transmission line is reversed compared to before transmission of the direction switching command. A transmission direction switching method for controlling switching of the two host I / O terminals.

Images