JPH06232881A - Time division multiplex communication system - Google Patents

Abstract

PURPOSE:To provide a time division multiplex communication system for decreasing load on the side of a main device when transmitting data between slave devices in the case of data transmission by polling. CONSTITUTION:The order of performing the data transmission of slave devices 1-14 to perform data transmission with a master device 21 by polling is decided in advance, the main device 21 transmits an idle signal command showing a state to be enable the data transmission with the slave device in place of a polling command, when the idle signal command is received, the slave devices 1-14 monitor signals on a transmission line 22, when the order of data transmission is turned to its own device and it is detected the other slave devices are in non-transmitting states, the address of the transmission party is designated, the data transmission with the slave device of this address and when the order of data transmission is turned to its own device and it is detected the other slave devices are set in transmitting states, the data transmission is waited for the next order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time division multiplex communication system for transmitting data by time division multiplex.

[0002]

2. Description of the Related Art In some communication systems for transmitting data by time division multiplexing, a plurality of slave devices are connected to one main device via a transmission path. Further, in this communication system, there is one in which a master device transmits data by polling with each slave device.

In data transmission by polling, a method is used in which a main device sequentially inquires of a slave device whether or not there is a transmission request, and the slave device responds to the request. There are the following methods for data transmission by this polling. When a slave device transmits, it sends an interrupt signal. The main device that received this signal,
Interrupt poll this slave to get the address of this slave. After this, the master polls this slave and receives data from this slave.

This method allows the slave device to transmit data to the master device. An example of such data transmission is described in JP-A-59-4356.

[0005]

By the way, in the case of data transmission by polling as described above, when data transmission is performed between slave devices, the main device receives data from one slave device once, The received data is transmitted to the other slave device.

For this data transmission, the main device side is
It is necessary to monitor the presence or absence of an interrupt during transmission, and address detection processing by interrupt polling is necessary. Further, when interrupt requests are issued from a plurality of slave devices, the main device side needs to perform transmission collision determination processing.

As a result, the processing on the slave device side is simplified, but the processing on the main device side is increased, and the load on the main device becomes heavy. For example, the slave device side can perform processing with a 4-bit microcomputer, but the main device side requires a 4-bit high-speed microcomputer or an 8-bit microcomputer, which increases the production cost of the main device. . In addition, since it is transmitted again from the master device to the slave device, it takes time.

An object of the present invention is to provide a time division multiplex communication system which can reduce the load on the main device side when data is transmitted between subordinate devices in data transmission by polling, except for such drawbacks. is there.

[0009]

In order to achieve the object of the present invention, a master device is connected to a plurality of slave devices via a transmission line, different addresses are assigned to the slave devices, and the master device is In a time division multiplex communication system in which data is transmitted by polling with each slave device, the slave device predetermines the order of data transmission, and the main device
Instead of the polling command, an idle signal command indicating that data transmission is possible between slave devices is transmitted.When the slave device receives an idle signal command, the slave device monitors the signal on the transmission path, and the data transmission order is determined by the slave device. When it is detected that another slave device is in the untransmitted state, the address of the other party is specified, data transmission is started with the slave device of this address, and the order of data transmission becomes the own device. In this case, when it detects that another slave device is in the transmission state, it waits until the next rank.

[0010]

Thus, when the master device transmits the idle signal command, each slave device detects that it is possible to perform data transmission with another slave device. After that, each slave device monitors the presence or absence of a signal on the transmission path.

When there is no signal on the transmission path at the time when the order of data transmission reaches its own device, this slave device specifies an address and transmits data to the slave device of this address. Further, when there is a signal on the transmission path at the time when the order of data transmission becomes its own device, this slave device waits until the next order of data transmission.

[0012]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a diagram of a communication system to which an embodiment of the present invention is applied. This communication system includes a main device 21 as a main station side that performs various controls during data transmission, a transmission line 22 that is two non-polar conductors connected to the main device 21, and this transmission line. It is composed of slave stations 1 to 14 as slave stations of 14 stations, which are connected to the slave station 22 and transmit data under the control of the master station 21.

In this communication system, data is transmitted in frames. Here, the frame transmitted from the main device 21 is the master frame, and the slave device 1
The frames transmitted from -14 are slave frames. The master frame and the slave frame are shown in FIG.

In the frame of FIG. 2, the start flag (F) 31 is transmitted first. The start flag 31 indicates the start of a frame. The start flag 31 is also used to detect that another slave device is transmitting. Further, the start flag 31 is used to set a reception timing between the main device 21 and the slave devices 1 to 14 during data transmission. Self address (SA) 32 transmitted next to the start flag 31
Indicates the address of its own device.

A partner address (DA) 33 transmitted next to the self address 32 is used for designating a partner device for communication. Further, the partner address 33 becomes a signal of a predetermined pattern when transmitting an idle signal indicating data transmission between slave devices. The idle signal command is distinguished from the polling command by the master frame including the partner address 33 of the predetermined pattern.

A control code (CC) 34 transmitted next to the partner address 33 conveys various control information.
Data transmitted next to the control code 34 (DA
TA) 35 defines how to use the application in the communication system of FIG. For example, slaves 1 to
When 14 is used for various controls, on / off control information of devices (not shown) connected to the slave devices 1 to 14 is transmitted by this data 35. Further, the information indicating the lighting state of the lamp and the information indicating the temperature and the humidity are transmitted by the data 35. Frame check sequence (FCS) 36 transmitted next to data 35
Is for detecting an error in a transmitted frame. That is, the frame check sequence 36 is
It is a redundant code for detecting or correcting a code error from the partner address 33 to the data 35.

In the communication system of FIG. 1 for transmitting data in the frame having the above-mentioned structure, the addresses are assigned to the slave devices 1, 2,
..., 14 in order. In addition, the slaves 1 to
In FIG. 14, the priorities for data transmission are determined, for example, in the order of addresses. That is, the highest rank is the slave 1, and the following ranks are the slaves 2, 3, ..., 1
It is 4. Further, the slaves 1 to 14 are assigned time slots, for example, in the order of addresses. As a result, in the communication system of FIG. 1, the subordinate device having the earlier time slot has a higher priority.

When such a communication system carries out data transmission, the main unit 21 on the main station side, as shown in FIG.
The time T _MF in a cycle of _SC, and transmits a command by the master frame. The cycle of T _SC for sending the master frame is a predetermined time. When sending this command, when not polling a specific slave device, the main device 21 sends a master frame in which the partner address 33 has a predetermined pattern, that is, a master frame indicating an idle signal command during the time T _MF. To do.

On the other hand, on the slave side, as shown in FIG.
Each of the slave devices 1 to 14 receives the master frame indicating the idle signal command transmitted during the _MF time. Upon receiving this master frame, the slave station waits only for the guard time of T _G1 . This guard time T _G1 is the time provided for the slave station to perform processing. As described above, the time slots TS1 to TS14 are assigned to the slave devices 1 to 14 on the slave station side in the order of addresses. Further, the slave device with the earlier time slot has a higher priority.

As a result, when the slave device 1 transmits data, it becomes as follows. That is, for example, when the state of a sensor (not shown) monitored by the slave device 1 changes, or when the open / closed state of a switch connected to the slave device 1 changes, the cycle connected to the slave device 1 for example, when a start timer has notified the lapse of the specified time, the expansion device 1, after the guard time T _G1 has passed,
The slave frame is transmitted by designating the address of the partner address 33. As a result, the subordinate device 1 having the first priority order directly performs data transmission with the designated subordinate device.

When the slave device N (2≤N≤14) transmits data, the following occurs. That is, the time slots TS1 to TS1 are assigned to the slaves 1 to 14 on the slave side.
Since TS14 is assigned, the slave device N
_The transmission path 22 is monitored during the time of _S · (N−1). This time T _{S is} a time for which the start flag 31 can be sufficiently detected. If a slave device having a higher priority than its own device transmits a slave frame during the time T _S · (N−1), the slave device N detects the start flag 31 of this frame. Wait for transmission. Then, it waits for transmission until the next time slot arrives. When this start flag 31 is detected, there is a possibility that it is a slave frame for its own device, so the slave device N performs the slave frame reception process.

When the start flag 31 is not detected and the time slot TSN (2.ltoreq.N.ltoreq.14) of the device itself, which is the Nth time slot, comes, the slave device N transmits a slave frame. As a result, the slave device N having the Nth priority directly performs data transmission with another slave device. After transmitting this slave frame, the time until the next master frame is transmitted from the main device 21 becomes the guard time. For example, in the slave device 3 having the third priority, as shown in FIG. 5, the guard device operates from the time T _SF when the slave device 3 transmits the slave frame to the time when the next master frame is transmitted. It is time T _G3 .

Furthermore, the subordinate device 1 having the 14th priority
In the data transmission of No. 4, as shown in FIG. 4, when the slave device 14 finishes the transmission of the slave frame at the time of T _SF and the guard time of T _G2 elapses, the main device 21 again.
Sends a master frame. The guard time T _{G2 at} this time is shorter than the guard time T _{G3 of the} third priority, for example, because the cycle T _SC is constant.

In this way, the time slots are assigned to the subordinate devices 1 to 14, the frame has the self address 32 and the partner address 33, and the time slot of the device having a higher priority than the self device is monitored. ,
When the master device 21 does not poll, the slave device on the slave station side can directly perform data transmission with another slave device. At this time, since the priorities of the respective slaves 1 to 14 are determined in advance, it is possible to prevent the two slaves from transmitting data at the same time. As a result, the main unit 21 has a conventional process of monitoring the presence or absence of an interrupt, an address detection process by interrupt polling,
There is no need for transmission collision determination processing.

Further, in the data transmission between the slave devices, the data is transmitted at high speed because it does not pass through the main device 21.

In this embodiment, as shown in FIG. 1, the main device 21 is connected to the slave devices 1 to 14 by a branching method, but the invention is not limited to this. For example, as shown in FIG. 6, the main unit 21 transmission lines 23 ₁ -
The present invention is also applied to a communication system of a switching system which is connected to the subordinate devices 1 to ₁₄ at 23 ₁₄ . Furthermore, the present invention is also applied to a communication system in which a branch system and a switching system are combined.

Further, in this embodiment, the slave device connected to the main device 21 is 14 stations, but it is not limited to 14 stations in particular.

Further, in this embodiment, the master frame is divided into the polling command and the idle signal command, but the present invention is not limited to this. For example, the polling command and the idle signal command are made the same. At this time, the subordinate device having a higher priority can transmit data in preference to polling the subordinate device having a lower priority.

[0030]

As described above, according to the present invention, the main device only transmits the idle signal command,
Allows data transmission between slaves. Further, since the order in which the subordinate devices transmit data is predetermined, it is possible to prevent a plurality of subordinate devices from starting data transmission at the same time. Therefore, since the processing provided in the conventional main device is not required for data transmission between the slave devices, the load on the main device can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a communication system for carrying out the present invention.

FIG. 2 is a diagram showing a configuration of a frame.

FIG. 3 is a diagram showing a transmission timing of a main device.

FIG. 4 is a diagram for explaining data transmission by a slave device.

FIG. 5 is a diagram for explaining data transmission by a slave device having a third priority.

FIG. 6 is a diagram showing another example of a communication system.

[Explanation of symbols]

 1-14 Subordinate device 21 Main device 22 Transmission path

Claims (1)

[Claims] 1. A time division system in which a master device is connected to a plurality of slave devices via transmission lines, different addresses are assigned to the slave devices, and the master device performs data transmission by polling with each slave device. In the multiplex communication system, the slave device predetermines the order of data transmission, the main device transmits an idle signal command indicating a state in which data transmission is possible between the slave devices instead of the polling command, and the slave device When the device receives the idle signal command, the device monitors the signal on the transmission path, and when the data transmission order becomes its own device, when it detects that another slave device is in the non-transmission state, When an address is specified and data transmission is started with the slave device of this address, and the priority of data transmission becomes its own device, another slave device sends it. A time-division multiplex communication system characterized by waiting for the next rank when it is detected that it is in a communication state.