JP2008227558A - Network adapter, communication terminal, communication path distribution method and program thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a network adapter which holds the LAN environment with a terminal on the end side, even if the power of a device configuring an LAN is turned off, and configure a network with a short network cable without requiring troublesome work for routing the network cable or confirming the connection place, and to also provide a communication terminal, and communication path distribution method and program. <P>SOLUTION: The network adapter 10 comprises a first port 111, a second port 112, a first network controller 121, a second network controller 122, a relay 13 for switching the signal path, and a relay control circuit 14 for controlling operation of the relay 13, based on the state of a communication terminal 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, in order to perform information communication by connecting a plurality of communication terminals via a LAN (Local Area Network) or the like, the present invention is connected to two external devices and connected to a communication terminal and communicates with the two external devices. The present invention relates to a network adapter that performs communication between terminals, a communication terminal, a communication path distribution method, and a program thereof.

  The LAN standard token ring standardized by the IEEE 802.5 committee is a typical example of performing information communication by connecting a plurality of communication terminals in a LAN. In the token ring, a ring type LAN is constructed by connecting communication devices in a ring shape, and a twisted pair cable is used as the LAN cable. A token passing system is adopted for access control, and "transmission right" data called a token always circulates in the network, and the terminal that has captured the data transmits the data.

  Also, in a system that connects communication devices and transmits / receives data within a limited range such as in a factory, office, or building, connection using 10BASE-T or 100BASE-TX is the mainstream, and there are three or more communication terminals. In the case of connection, a concentrator called a hub is indispensable for concentrating cables connected to a plurality of terminal devices and switching them.

  For example, as a token ring LAN hub used in the token ring LAN shown in FIG. 6, as shown in FIG. 7, a power supply monitoring circuit 55 for monitoring the power supply 51 of the hub and a LAN management circuit according to the monitoring result. A LAN management circuit bypass relay 53 for bypassing the hub internal transmission paths 56 to 59 from the station 52 to the stations 64a to 66d, and a blocking circuit 60 for blocking requests from the stations 64a to 64d to the phantom circuit 61 according to the monitoring results. What provided is known. (For example, see Patent Document 1)

By applying this conventional technique, when the power supply of a certain terminal 73C becomes malfunctioning on the token ring LAN of FIG. 6, the power supply monitoring circuit 55 detects that the power supply 51 of the hub cannot output stable power. Then, the LAN management circuit bypass relay 53 is switched, and the LAN management circuit 52 enters the bypass state. Therefore, the station is separated from the LAN management circuit 52 that cannot normally perform frame relay, and at the same time, the blocking circuit blocks the request from the station to the phantom circuit. Therefore, even if there is a subscription request from the station, the hub leaves the token ring network, and system down due to unstable power supply is avoided.
Japanese Patent Laid-Open No. 06-014036 (page 3, FIG. 1, FIG. 3)

However, in the conventional technology, when connecting a plurality of communication terminals to a LAN, the network cables from the plurality of communication terminals are concentrated on one hub, and the communication terminals are used in a factory, office, or building. When the network is scattered, a long network cable may be required for network construction. In addition, it is necessary to secure an appropriate space for bundling the cables, and complicated work is required for handling the network cable and confirming the connection destination.
Further, the token ring LAN hub disclosed in Patent Document 1 must be used in a state where the hub power supply is always turned on in order to maintain the LAN, and the power supply of the hub 73c in FIG. In such a case, there is a problem that the terminals 74e and 74f on the end side are isolated from the LAN and isolated.

  Therefore, in the present invention, even when the device for constructing the LAN is turned off, the LAN environment with the terminal on the terminal side is maintained, and the network cable is routed and the connection destination is confirmed. An object of the present invention is to provide a network adapter, a communication terminal, a communication path distribution method, and a program thereof that can construct a network with a short network cable without requiring work.

In order to solve the above problems, the present invention is configured as follows.
The invention according to claim 1 is a network adapter for a communication terminal that is network-connected to two external devices and connected to a communication terminal, and performs communication between the two external devices and the communication terminal. A first port for network connection with the first external device, a second port for network connection with the second external device, a first network controller for communicating with the communication terminal, and communication with the communication terminal A second network controller for switching a signal path between the first port, the second port, the first network controller, and the second network controller, and the relay based on a state of the communication terminal A relay control circuit for controlling the operation of the first network controller. A first communication state in which the first port and the communication terminal communicate with each other via the second network controller and the second port communicates with the communication terminal via the second network controller; and the first port And the second communication state in which direct communication is performed between the second port and the relay control circuit, the relay control circuit switches the relay to the first communication state when the communication terminal is operating normally. In other cases, the relay is controlled so as to be in the second communication state.

In the invention according to claim 2, the relay control circuit is configured to be in a first communication state when the power of the communication terminal is on, and to be in a second communication state at other times. The relay is controlled.
According to a third aspect of the present invention, when the normal signal is input as the watchdog timer signal of the communication terminal, the relay control circuit is in the first communication state, and otherwise the second control state is the second communication state. The relay is controlled so as to be in a communication state.
According to a fourth aspect of the present invention, the relay control circuit is in a first communication state when the power of the communication terminal is on and a normal signal is input as the watchdog timer signal. In other cases, the relay is controlled to be in the second communication state.
According to a fifth aspect of the present invention, the network adapter for the communication terminal has a structure that can be detachably attached to the communication terminal, and when the network adapter is removed from the communication terminal, the second communication state is established. It is characterized by this.

The invention according to claim 6 is connected to the network adapter for the communication terminal according to any one of claims 1 to 5, and is connected to two external devices via the network adapter for the communication terminal. A communication terminal that performs communication includes a network adapter for the communication terminal and a data distribution unit that distributes a communication path between the communication terminals, and the data distribution unit receives a communication signal from the first network controller. Analyzes the address which is the destination of the communication signal, and if the address is addressed to the own terminal, takes the communication signal into the own terminal, otherwise transfers the communication signal to the second network controller. When a communication signal is received from the second network controller, the address that is the destination of the communication signal is analyzed and the address is If the communication address is addressed to the own terminal, the communication signal is taken into the own terminal. Otherwise, the communication signal is transferred to the first network controller, and the communication signal is transmitted from the own terminal to the first external device. When the communication signal is transmitted to the first network controller, and when the communication signal is transmitted from the terminal to the second external device, the communication signal is transmitted to the second network controller. It is.
The invention according to claim 7 further includes a watchdog timer that monitors a communication state of the data distribution unit and transmits a normal signal to the network adapter for the communication terminal only when the communication state is normal. It is characterized by comprising.

  The invention according to claim 8 is connected to the network adapter for the communication terminal according to any one of claims 1 to 5, and two external devices are connected via the network adapter for the communication terminal. In the communication path distribution method of a communication terminal that performs communication, when the communication terminal receives a communication signal from the first network controller, the address that is the destination of the communication signal is analyzed, and the address is addressed to its own terminal When the communication signal is received from the second network controller, the step S1 for fetching the communication signal into the own terminal, otherwise the step S2 for transferring the communication signal to the second network controller. When the address which is the destination of the communication signal is analyzed and the address is addressed to the own terminal, the communication signal is stored in the own terminal. Step S3 for entering, Step S4 for transferring the communication signal to the first network controller if not, and Step S3 for transmitting the communication signal from the terminal to the first external device. Step S5 for transmitting to the controller and step S6 for transmitting the communication signal to the second network controller when the communication signal is transmitted from the own terminal to the second external device are provided.

According to a ninth aspect of the present invention, there is provided a step of determining whether or not any of the steps from Step S1 to Step S6 has ended normally, and if the step has ended normally, the watchdog timer The normal signal is transmitted to the watchdog timer if it is normal, and if not normal, the normal signal is transmitted to the watchdog timer. The method further comprises the step of causing the watchdog timer to stop transmitting the normal signal.
The invention described in claim 10 is connected to the network adapter for the communication terminal according to any one of claims 1 to 5, and is connected to two external devices via the network adapter for the communication terminal. A communication terminal program for performing communication, wherein the communication path distribution method according to claim 8 or 9 is implemented.

According to the first aspect of the present invention, the network adapter includes a relay that switches a signal path between the first port, the second port, the first network controller, and the second network controller, and the relay that is based on the state of the communication terminal. A relay control circuit for controlling the operation of the first communication port, the relay communicates with the first port via the first network controller, and communicates with the second port via the second network controller. Switching between a first communication state in which the terminal communicates and a second communication state in which direct communication is performed between the first port and the second port, the relay control circuit is configured so that when the communication terminal is operating normally, Since the relay is controlled so as to be in the first communication state, and in other cases, the relay is controlled so as to be in the second communication state. Communication by the second communication state even if it is not normal can hold.
According to the second to fourth aspects of the present invention, the relay control circuit is in the first communication state when the power of the communication terminal is on or when a normal signal is input as a watchdog timer signal. In other cases, the relay is controlled so as to be in the second communication state, so that the communication state can be switched using either or both of the power-off and the watchdog timer signal.

According to the fifth aspect of the present invention, the network adapter has a structure that can be detachably attached to the communication terminal. When the network adapter is detached from the communication terminal, the network adapter is in the second communication state. The environment can be maintained.
According to the invention described in claims 6 and 8, when the communication terminal receives the communication signal, if the address that is the destination of the communication signal is addressed to the own terminal, the communication signal is placed in the own terminal. Otherwise, since the communication signal is passed, the communication terminal acts as a hub, and the communication terminal can connect a plurality of units without directly connecting a network cable to the hub.
According to the invention of claim 7 and claim 9, the watchdog timer for monitoring the communication state of the data distribution unit in the communication terminal and transmitting a normal signal to the network adapter only when the communication state is normal is provided. Furthermore, since it is provided, the LAN environment can be maintained even when the communication state is abnormal.
In this way, even when the power of the device for constructing the LAN is turned off, the LAN environment with the terminal on the terminal side is maintained. In addition, a LAN configuration in which a plurality of network adapters and communication terminals are connected in a daisy chain is possible, and a network can be constructed with a short network cable without requiring complicated operations such as routing of the network cable and confirmation of the connection destination.

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

FIG. 1 is a diagram illustrating a configuration of a communication terminal and a network adapter for the communication terminal according to the present invention. In FIG. 1, the communication terminal 20 performs information communication with the first external device 301 and the second external device 302 via the network adapter 10 connected by a LAN cable 303.
The network adapter 10 includes a first port 111 for network connection with the first external device 301, a second port 112 for network connection with the second external device 302, and a first network controller for communicating with the communication terminal 20. 121, second network controller 122, first port 111, second port 112, first network controller 121, relay 13 for switching LAN signals of second network controller 122, and relay 13 based on the state of communication terminal 20 And a relay control circuit 14 for controlling.
For example, when the relay 13 has a 4-core LAN cable, the LAN signal is switched at the four contacts 131 to 134 so as to correspond to the relay cable. That is, a first communication state in which the first port communicates with the communication terminal 20 via the first network controller, and the second port communicates with the communication terminal 20 via the second network controller; The second communication state in which direct communication is performed between the port 111 and the second port 112 is switched.
The first network controller 121 and the second network controller 122 convert a LAN signal and a signal for a communication terminal such as a bus signal. For example, pulse transformers 121A and 122A, Ethernet (registered trademark) PHY (Physical) Layer (physical layer) 121B, 122B, Ethernet (registered trademark) MAC (Media Access Control) 121C, 122C.
The communication terminal 20 includes a power supply 28, a power supply monitoring circuit 22, a watchdog timer 21, and a data distribution unit 27 that distributes communication path data. The data distribution unit 27 includes, for example, a CPU 23, a ROM 24, a RAM 25, and a CPU bus 26, which are general configurations of a personal computer. Note that an arithmetic processing unit such as a microcomputer may be used instead of the CPU 23.

FIG. 2 is a diagram for explaining the first communication state and the second communication state.
In the first communication state, as shown in FIG. 2A, the second port 112 and the second network controller 122 are connected via the contact 131, and the first port 111 and the first network are connected. A controller 121 is connected. On the other hand, in the second communication state, the first port 111 and the second port 112 are connected via the contact 131 as shown in FIG. In the figure, only the contact 131 is shown, but the same applies to the contacts 132 to 134.

The relay 13 is controlled by a relay control circuit 14. The relay control circuit 14 controls the relay 13 so as to be in the first communication state only when the communication terminal 20 is normally operating, and in other cases, the relay control circuit 14 is set so as to be in the second communication state. 13 is controlled.
For example, the relay 13 is controlled via the relay control circuit 14 with a signal from a power monitoring circuit 22 that monitors a power supply abnormality of the communication terminal 20 and a watchdog timer 21 that detects an abnormal operation of the communication terminal 20. If the power supply 20 is on and the signal of the watchdog timer 21 is input as a normal signal, the first communication state is set. Otherwise, the second communication state is set. Good. By doing so, the watchdog timer 21 periodically monitors the communication status and the power supply monitoring circuit 22 instantly senses power off, so that immediately when the communication terminal is not operating normally or when power is shut off. It is switched to the second communication state. For this reason, a stable LAN environment is maintained.

In addition, although illustration is omitted, the relay 13 may be controlled based only on the power supply of the communication terminal 20 without providing the watchdog timer 21. In this case, even in a communication terminal without a watchdog timer structure, if the relay control circuit 14 has the function of the power supply monitoring circuit 22, the software configuration is changed without changing the hardware configuration of the communication terminal 20. The object of the present invention can be achieved.
Although not shown, the relay 13 may be controlled based only on the signal of the watchdog timer 21 without providing the power supply monitoring circuit 22. In this case, the structure of the network adapter 10 and the communication terminal 20 can be simplified.

  With the configuration described above, information communication between the first external device 301 and the communication terminal 20 and information communication between the second external device 302 and the communication terminal 20 are performed only when the communication terminal 20 is operating normally. When the communication terminal 20 is not operating normally or the power is off, information communication between the first external device 301 and the second unit device 302 is performed directly, and the LAN environment is maintained.

In addition, the network adapter 10 and the communication terminal 20 can be connected to each other through a LAN.
FIG. 3 is a diagram illustrating a connection example of a plurality of network adapters and communication terminals. Here, 10A to 10D are network adapters, 20A to 20D are communication terminals, and the network adapters 10A to 10D are connected by a LAN cable 303. One end of the network adapter 10 </ b> A is connected to the hub 31. By connecting in this way, it is possible to construct a network with a short network cable 303 without requiring complicated work such as handling of the network cable 303 and confirmation of the connection destination.
When the communication terminal 20A is not operating normally, the network adapter 10A is in the second communication state, and the hub 31 and the communication terminal 20B are substantially directly connected via the LAN.
In other words, when building a network by connecting communication terminals, the network adapter and the communication terminal act as the hub, and the communication terminal can connect multiple units without directly connecting the network cable to the hub. It becomes possible.

The network adapter 10 is preferably configured to be detachable from the communication terminal 20, such as a card-type adapter. When the network adapter 10 is removed from the communication terminal 20, the second communication state can be maintained because the communication terminal 20 is not operating normally.
For example, even if the network adapter 10C is removed from the communication terminal 20C in FIG. 3, if the LAN cable 303 is left connected to the network adapter 10C, the LAN environment can be maintained, and only the communication terminal 20C can be connected from the LAN. It can be removed temporarily and carried around.
The network adapter 10 may be connected to the communication terminal 20 via a USB (Universal Serial Bus) by providing a USB interface.
Note that the relay control circuit 14, the first network controller 121, and the second network controller 122 are more preferably supplied with the power supply 28 from the communication terminal 20.

Next, communication route distribution processing for distributing communication signal routes at the communication terminal 20 will be described.
When the data distribution unit 27 receives a communication signal from the first network controller 121, the data distribution unit 27 analyzes the address that is the communication destination, and when the address is addressed to the own terminal, the data distribution unit 27 sends the communication signal to the own terminal. If not, the communication signal is transferred to the second network controller 122.
When a communication signal is received from the second network controller 122, the address as the communication destination is analyzed, and when the address is addressed to the own terminal, the communication signal is taken into the communication terminal 20, otherwise The communication signal is transferred to the first network controller 121.
When a communication signal is transmitted from the communication terminal 20 to the first external device 301, the communication signal is transmitted to the first network controller 121.
When a communication signal is transmitted from the communication terminal 20 to the second external device 122, the communication signal is transmitted to the second network controller 122.
As described above, the communication path distribution process has a function of switching the communication path between the first network controller 121, the second network controller 122, and the communication terminal 20, and the function is realized by software processing, for example. The

That is, data input from the first port 111 or the second port 112 is converted into a signal by the first or second network controller 121, 122 and stored in the ROM 24 or RAM 25 via the CPU bus 26 of the communication terminal 20. Is processed by the program of the data distribution unit 27.
When information is transmitted from the communication terminal 20 to the first or second external device 301 or 302, the same processing is performed by the program.

FIG. 4 shows a flowchart of the communication path distribution method of the present invention. This method is implemented by a program of the data distribution unit 27 of the communication terminal 20.
When a LAN signal is input from the first port 111 in step S101, the first network controller 121 performs signal conversion from a LAN signal to a communication signal for a communication terminal such as a bus signal in step S102. In step S <b> 103, the communication terminal 20 receives a communication signal from the first network controller 121. In step S104, the data distribution unit 27 analyzes the address that is the destination of the communication signal. If the address is addressed to the own terminal, the communication signal is taken into the own terminal in step S105. On the other hand, when the address is not addressed to the own terminal, the process proceeds to step S201, and the communication signal is transferred to the second network controller 122. In step S202, the second network controller 122 performs signal conversion from a communication signal for the communication terminal 20 to a LAN signal. In step S203, a LAN signal is output from the second port 112.
Here, if the communication terminal 20 receives a communication signal via the first network controller 121 and the communication signal is destined for the own terminal, the step of taking in the signal is set to S1, and if not, the second step is taken. The step of transferring to the network controller 122 is S2. That is, step S1 is configured by S103, S104, and S105, and step S2 is configured by S103, S104, and S201.

When a LAN signal is input from the second port 112 in step S301, the second network controller 122 performs signal conversion from the LAN signal to a communication signal for a communication terminal such as a bus signal in step S302. In step S <b> 303, the communication terminal 20 receives a communication signal from the second network controller 122. In step S304, the data distribution unit 27 analyzes the address that is the destination of the communication signal. If the address is addressed to the own terminal, the communication signal is taken into the communication terminal 20 in step S305. On the other hand, when the address is not addressed to the own terminal, the process proceeds to step S 401, and the communication signal is transferred to the first network controller 121. In step S402, the first network controller 121 performs signal conversion from a communication signal for the communication terminal 20 to a LAN signal. In step S403, a LAN signal is output from the first port 111.
Here, the communication terminal 20 receives a communication signal via the second network controller 122, and if the signal is addressed to the own terminal, the step of capturing the communication signal is set to S3. The step of transferring to the network controller 121 is S4. That is, S303, S304, and S305 constitute step S3, and S303, S304, and S401 constitute step S4.

When a LAN signal is to be transmitted from the terminal to the first external device 301, the communication terminal 20 generates a communication signal in step S501. In step S 502, the data distribution unit 27 adds an address to the communication signal and transfers it to the first network controller 121. In step S503, the first network controller 121 performs signal conversion from a communication signal for the communication terminal 20 to a LAN signal. In step S504, a LAN signal is output from the first port 111.
When a LAN signal is to be transmitted from the own terminal to the second external device 302, the communication terminal 20 generates a communication signal in step S601. In step S 602, the data distribution unit 27 adds an address to the communication signal and transfers it to the second network controller 122. In step S603, the second network controller 122 performs signal conversion from a communication signal for the communication terminal 20 to a LAN signal. In step S604, a LAN signal is output from the second port 112.
Here, steps S501 and S502 in which the communication terminal 20 generates a communication signal, adds an address to the communication signal, and transfers this to the first network controller 121 are set as step S5, and are transferred to the second network controller 122 in step S601. , S602 is defined as step S6.
Signal distribution in the communication terminal 20 is realized by the communication path distribution method according to the above steps S1 to S6.
Note that when the communication terminal 20 does not know which of the first external device 301 and the second external device 302 should transmit the LAN signal, it is only necessary to execute both step S5 and step S6 for the LAN signal.

  Next, the function of the watchdog timer 21 will be described. When the communication terminal 20 does not operate normally, communication between the first external device 301 and the second external device 302 cannot be performed, and the LAN environment is not maintained by blocking the communication path. In order to avoid this, the watchdog timer 21 periodically monitors the operation of the communication terminal 20 by confirming that a predetermined normal signal is sent from the CPU 23.

When the network adapter 10 monitors both the power supply monitoring circuit 22 and the watchdog timer 21, the second communication is performed until the power supply of the network adapter 10 is turned on and the power supply monitoring circuit 22 of the communication terminal 20 outputs normally. In this state, after the power is turned on, the power monitoring circuit 22 outputs a normal signal, and when the program stored in the ROM 24 or RAM 25 is activated and the communication terminal 20 becomes communicable, the watchdog timer 21 is normal. A signal is output, and the relay 13 is controlled so that the relay control circuit 14 shifts to the first communication state.
Thereafter, the power supply monitoring circuit 22 outputs a normal signal to the relay control circuit 14 only when the power supply voltage is normal. When a power supply voltage abnormality or the like is detected, an abnormality signal is output to the relay control circuit 14, and the relay control circuit 14 switches the relay 13 to the second communication state.
Further, the watchdog timer 21 outputs a normal signal to the relay control circuit 14 if a normal access is received from the CPU 23 within a certain hour. If normal access does not come from the CPU 23 within a certain hour, an abnormal signal is output to the relay control circuit 14, and the relay control unit 14 switches the relay 13 to the second communication state.

Here, the control of the watchdog timer 21 is processed by a program stored in the data distribution unit 27 as part of the communication path distribution method.
FIG. 5 is a flowchart of watchdog timer control.
In step S11, it is determined whether or not any of the steps from step S1 to step S6 in FIG. 4 has ended normally. If the processing has ended normally, the process proceeds to step S13, and a normal signal is transmitted to the watchdog timer 21. Let If not completed normally, the process proceeds to step S12, and the state of the data distribution unit 27 is checked. If the data distribution unit 27 is normal, the process proceeds to step S13. If not normal, the process proceeds to step S14, where the watchdog timer 21 stops sending a normal signal.
In addition, the watchdog timer is not controlled by the program in this way, but the CPU accesses the watchdog timer within a certain period of time, and when the access stops, the watchdog timer transmits an abnormal signal. It is also possible.

  Thus, according to the present invention, the LAN environment with the terminal on the terminal side is maintained even when the power of the device for constructing the LAN is turned off. In addition, a LAN configuration in which a plurality of network adapters and communication terminals are connected in a daisy chain is possible, and a network can be constructed with a short network cable without requiring complicated operations such as routing of the network cable and confirmation of the connection destination.

  As the communication terminal to which the present invention is used, it is possible to use it in a factory-connected FA device or a personal computer connected in a LAN at work or school, and by using the network adapter of the present invention. The effects and effects described in the embodiments are exhibited.

The figure which shows the structure of the network adapter for the communication terminal and communication terminal of this invention The figure explaining the 1st communication state and the 2nd communication state Diagram showing connection example of multiple network adapters and communication terminals Flowchart of communication path distribution method of the present invention Flow chart of watchdog timer control The figure which shows the structure of the conventional token ring LAN The figure which shows the structure of the hub for the conventional token ring LAN

Explanation of symbols

10, 10A to 10D Network adapter 111 First port 112 Second port 121 First network controller 122 Second network controller 121A, 121B Pulse transformer 122A, 122B Ethernet (registered trademark) PHY
123A, 123B Ethernet (registered trademark) MAC
13 Relay 131, 132, 133, 134 Contact 14 Relay control circuit 20, 20A-20D Communication terminal 21 Watchdog timer 22 Power supply monitoring circuit 23 CPU
24 ROM
25 RAM
26 CPU bus 27 Data distribution unit 28 Power supply 31, 50, 73a to 73f Hub 301, 302 External device 303 LAN cable 51 Power supply 52 LAN management circuit 53 LAN management circuit bypass relay 54 Relay drive circuit 55 Power supply monitoring circuit 60 Shutdown circuit 61 Phantom Circuit 62a-62d Hub internal relay 63a-63d Hub internal relay switching circuit 64a-64d, 74a-74l Station 65a-65d Station internal phantom circuit 71 Main ring 72a-72c Concentrator

Claims (10)

In a network adapter for a communication terminal that is connected to a network with two external devices and connected to a communication terminal, and communicates between the two external devices and the communication terminal.
A first port for network connection with a first external device;
A second port for network connection with a second external device;
A first network controller for communicating with the communication terminal;
A second network controller for communicating with the communication terminal;
A relay for switching a signal path between the first port, the second port, the first network controller, and the second network controller;
A relay control circuit for controlling the operation of the relay based on the state of the communication terminal,
The relay is configured such that the first port communicates with the communication terminal via the first network controller, and the second port communicates with the communication terminal via the second network controller. Communication status of
Switching between a second communication state in which direct communication is performed between the first port and the second port;
The relay control circuit controls the relay so as to be in a first communication state when the communication terminal is operating normally, and otherwise controls the relay so as to be in a second communication state. A network adapter for a communication terminal characterized by controlling.   The relay control circuit controls the relay so as to be in a first communication state when the power of the communication terminal is on, and to be in a second communication state otherwise. The network adapter for communication terminals according to 1.   The relay control circuit controls the relay so as to be in a first communication state when a normal signal is input as a watchdog timer signal of the communication terminal, and to be in a second communication state otherwise. The network adapter for a communication terminal according to claim 1.   The relay control circuit is in a first communication state when the power of the communication terminal is on and a normal signal is input as the watchdog timer signal, and in a second communication state otherwise The network adapter for a communication terminal according to claim 1, wherein the relay is controlled as follows.   The network adapter for the communication terminal has a structure that can be detachably attached to the communication terminal, and when the network adapter is removed from the communication terminal, the network adapter is in a second communication state. 5. A network adapter for a communication terminal according to any one of 4 above. In a communication terminal connected to the network adapter for a communication terminal according to any one of claims 1 to 5 and communicating with two external devices via the network adapter for the communication terminal,
A data distribution unit that distributes a communication path between the network adapter for the communication terminal and the communication terminal;
When receiving a communication signal from the first network controller, the data distribution unit analyzes an address that is the destination of the communication signal. When the address is addressed to the own terminal, the data distribution unit Otherwise, the communication signal is transferred to the second network controller, and when the communication signal is received from the second network controller, the address that is the destination of the communication signal is analyzed, and the address is automatically determined. When the terminal is addressed to the terminal, the communication signal is taken into the terminal itself; otherwise, the communication signal is transferred to the first network controller, and the communication signal is transmitted from the terminal to the first external device. When the communication signal is transmitted to the first network controller and the communication signal is transmitted from the terminal to the second external device, the communication signal is transmitted. Communication terminal characterized by transmitting to the second network controller.   The watchdog timer according to claim 6, further comprising a watchdog timer that monitors a communication state of the data distribution unit and transmits a normal signal to the network adapter for the communication terminal only when the communication state is normal. Communication terminal. A communication path distribution method for a communication terminal connected to the network adapter for a communication terminal according to any one of claims 1 to 5 and communicating with two external devices via the network adapter for the communication terminal. ,
When the communication terminal receives a communication signal from the first network controller, it analyzes the address that is the destination of the communication signal. When the address is addressed to the own terminal, the communication signal is taken into the own terminal. Step S1,
If not, step S2 of transferring the communication signal to the second network controller;
When receiving a communication signal from the second network controller, analyze the address that is the destination of the communication signal, and when the address is addressed to the own terminal, step S3 to capture the communication signal in the own terminal;
Otherwise, step S4 for transferring the communication signal to the first network controller;
When transmitting a communication signal from the own terminal to the first external device, step S5 for transmitting the communication signal to the first network controller;
A communication path distribution method comprising: step S6 of transmitting the communication signal to a second network controller when transmitting a communication signal from the terminal to the second external device.
Determining whether any of the steps from step S1 to step S6 has successfully completed the process;
If the watchdog timer ends normally, sending the normal signal to the watchdog timer;
If not completed normally, the status of the data distribution unit is checked. If normal, the normal signal is transmitted to the watchdog timer, and if not normal, the normal signal is transmitted to the watchdog timer. The communication path distribution method according to claim 8, further comprising the step of stopping. A program for a communication terminal that is connected to the network adapter for a communication terminal according to any one of claims 1 to 5 and communicates with two external devices via the network adapter for the communication terminal. ,
A program for a communication terminal, which implements the communication path distribution method according to claim 8 or 9.

Images