JP2016082351A - Communications system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system capable of simplifying a system configuration resulting in a cost reduction.SOLUTION: When a master unit 10 determines that a communication with a follower unit 20 is not available based on a response/non-response to a communication signal transmitted to the follower unit 20 from a follower unit 20, the master unit 10 switches the output level for transmitting the communication signal to the follower unit 20 to an output level, which is different from the output level at a timing when non communication is made, during the communication with the follower unit 20 is available. When the output level which is switched by the master unit 10 continues for a certain period of time, the follower unit 20 resets.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication system in which communication is performed between a master device and a slave device, and the master device resets the slave device.

  2. Description of the Related Art Conventionally, there is known a communication system that includes a master device that controls the entire system and a slave device that controls peripheral functions, and performs communication between microcomputers mounted on each device. In the communication system configured as described above, a reset communication line is necessary for the main apparatus to reset the microcomputer of the slave apparatus, so that the system configuration becomes complicated and the cost due to the increase in the communication lines increases. There was a problem.

  In the conventional communication system disclosed in Patent Document 1 as a countermeasure for such a problem, when the microcomputer of the slave device is reset, it is transmitted from the master device to the slave device via the data communication line by the prohibiting means in the master device. Data transmission is prohibited, the reset signal is sent to the data communication line by the reset signal sending means in the main device, the reset signal is detected by the detecting means in the slave device, and the reset signal is detected by the detecting means As a result, the reset means in the slave device resets the slave device. Thus, since the reset signal is transmitted through the data communication line, the slave device can be reset without providing a reset communication line which is a dedicated line for sending the reset signal.

JP 2003-92611 A

  However, in the system shown in Patent Document 1, it is necessary to assign a dedicated port for outputting a reset signal in addition to the data transmission port to the microcomputer in the main apparatus, so that the system configuration is simplified and the cost is further increased. It was difficult to achieve reduction.

  The present invention has been made in view of the above, and an object of the present invention is to provide a communication system capable of simplifying the system configuration and further reducing the cost.

  In order to solve the above-described problems and achieve the object, the present invention provides a communication system in which a master device and a slave device transmit communication signals to each other via a communication line, and the master device includes: When it is determined that communication with the slave device is impossible due to the presence or absence of a reply from the slave device with respect to the communication signal transmitted to the slave device, the output level at which the communication signal is transmitted to the slave device is set to the communication with the slave device. Switch to an output level different from the output level at the timing when communication is not performed in a possible state, and the slave device resets the slave device when the output level switched by the master device continues for a certain period of time. It is characterized by.

  According to the present invention, it is possible to simplify the system configuration and further reduce the cost.

The figure showing the whole structure of the communication system which concerns on embodiment of this invention The figure showing the example of composition of the transmission and reception signal composition circuit The figure showing another example of composition of a transmission / reception signal composition circuit The figure which shows the structural example of a delay circuit The figure for demonstrating the relationship between the waveform of the communication signal output from Tx terminal of the microcomputer for main apparatuses, and the input level of Reset terminal

  Hereinafter, a communication system according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram showing the overall configuration of a communication system according to an embodiment of the present invention. The communication system includes a master device 10 and a slave device 20, and the master device 10 and the slave device 20 are connected to each other by a communication line 30 and a power line 31. The main device 10 includes a main device microcomputer 11 and a transmission / reception signal combining circuit 12, and the sub device 20 includes a sub device microcomputer 21, a transmission / reception signal combining circuit 22, a delay circuit 23, and a reset circuit 24. .

  The main device microcomputer 11 has a Tx terminal that is an output port of a communication signal transmitted from the main device 10 to the slave device 20, and an Rx terminal that is an input port of a communication signal transmitted from the slave device 20 to the main device 10. Have. The Tx terminal and the Rx terminal of the main device microcomputer 11 are connected to the transmission / reception signal combining circuit 12. The slave device microcomputer 21 includes a Tx terminal that is an output port of a communication signal transmitted from the slave device 20 to the master device 10, and an Rx terminal that is an input port of a communication signal transmitted from the master device 10 to the slave device 20. A Reset terminal. A transmission / reception signal combining circuit 22 is connected to the Tx terminal and the Rx terminal of the slave microcomputer 21, and a delay circuit 23 and a reset circuit 24 are connected to the Reset terminal. The transmission / reception signal combining circuit 12 and the transmission / reception signal combining circuit 22 are connected by a communication line 30. In FIG. 1, the Tx terminal is represented as “Tx”, the Rx terminal as “Rx”, and the Reset terminal as “Reset”.

  FIG. 2 is a diagram illustrating a configuration example of the transmission / reception signal combining circuits 12 and 22. The transmission / reception signal synthesizing circuits 12 and 22 are configured to include a transistor 201 whose base is connected to a Tx terminal and a transistor 202 whose base is connected to the collector of the transistor 201.

  The operation of the transmission / reception signal combining circuit shown in FIG. 2 will be described. Here, in order to simplify the description, an operation when a communication signal is transmitted from the main device microcomputer 11 to the sub device microcomputer 21 will be described. When the main unit microcomputer 11 does not communicate with the sub unit microcomputer 21 or when the main unit microcomputer 11 outputs the transmission data 1 to the sub unit microcomputer 21, the data is output from the Tx terminal of the main unit microcomputer 11 The output level of the communication signal to be transmitted is a high level. At this time, since the transistor 201 and the transistor 202 are turned off, the signal output levels of the transmission / reception signal synthesizing circuits 12 and 22 are at a high level.

  On the other hand, when the main device microcomputer 11 outputs the transmission data 0 to the slave device microcomputer 21, the output level of the communication signal output from the Tx terminal of the main device microcomputer 11 becomes the Low level, and the transistor 201 and the transistor 202 are output. Is turned on. Therefore, the signal output level of the transmission / reception signal synthesizing circuit 12 becomes a low level, and the signal output level of the transistor 202 is input to the Rx terminal of the microcomputer 11 for the main apparatus. The transmission / reception signal synthesis circuit 12 and the transmission / reception signal synthesis circuit 22 are connected to the open collector output of each transistor 202. Therefore, when the output of the Tx terminal is low level at the timing when one microcomputer performs transmission, Although the output of the Tx terminal is at a high level at the timing received by the microcomputer, the high level output is short-circuited and the Tx terminal of the microcomputer is not damaged by an overcurrent.

  FIG. 3 is a diagram illustrating another configuration example of the transmission / reception signal synthesis circuit. The transmission / reception signal combining circuit 12A includes a transistor 303, a photocoupler 301 having a Tx terminal connected to the primary side and a base of the transistor 303 connected to the secondary side, and a transistor 303 connected to the primary side. And a photocoupler 302 to which the Rx terminal is connected. The transmission / reception signal combining circuit 12A of FIG. 3 is used for the main device 10 and the transmission / reception signal combining circuit 22 of FIG. 2 is used for the slave device 20, whereby insulation between the main device 10 and the slave device 20 is achieved. 3 may be used instead of the transmission / reception signal combining circuit 22 of the slave device 20.

  The operation of the transmission / reception signal combining circuit 12A shown in FIG. 3 will be described. Here, in order to simplify the description, an operation when a communication signal is transmitted from the main device microcomputer 11 to the sub device microcomputer 21 will be described. When the main unit microcomputer 11 does not communicate with the sub unit microcomputer 21 or when the main unit microcomputer 11 outputs the transmission data 1 to the sub unit microcomputer 21, the data is output from the Tx terminal of the main unit microcomputer 11 The output level of the communication signal to be transmitted is a high level. At this time, since the primary side of the photocoupler 301 becomes non-conductive, the secondary side of the photocoupler 301 is turned off, and the signal output level of the transmission / reception signal combining circuit 12A becomes High level.

  On the other hand, when the main apparatus microcomputer 11 outputs transmission data 0 to the sub apparatus microcomputer 21, the output level of the communication signal output from the Tx terminal of the main apparatus microcomputer 11 becomes the Low level. Therefore, the primary side of the photocoupler 301 is turned on, the secondary side of the photocoupler 301 is turned on, and the signal output level of the transmission / reception signal combining circuit 12A becomes the low level.

  Conversely, when the main device microcomputer 11 receives the signal, the signal from the device microcomputer 21 is input according to the communication signal output of the transmission / reception signal combining circuit 12A. When the slave device microcomputer 21 outputs the transmission data 1 to the master device microcomputer 11, the communication signal output becomes High level and the transistor 303 is turned off. Since the transistor 303 is turned off, the primary side of the photocoupler 302 is turned off, the secondary side of the photocoupler 302 is turned off, and a high level voltage is applied to the Rx terminal of the main device microcomputer 11.

  On the other hand, when the slave device microcomputer 21 outputs the transmission data 0 to the master device microcomputer 11, the communication signal output is at the low level. Therefore, the primary side of the photocoupler 301 becomes conductive, the secondary side of the photocoupler 301 is turned on, and a Low level voltage is applied to the Rx terminal of the main device microcomputer 11.

  FIG. 4 is a diagram illustrating a configuration example of the delay circuit 23. FIG. 4 shows a slave device microcomputer 21, a delay circuit 23, and a reset circuit 24 that constitute the slave device 20. The delay circuit 23 is connected to the connection terminal between the Reset terminal and the reset circuit 24 of the slave device microcomputer 21. Has been.

  The delay circuit 23 includes a transistor 401 whose base is input with a communication signal transmitted from the main apparatus 10 via the communication line 30 of FIG. 1, a capacitor 404 whose one end is connected to the transistor 401 and whose other end is grounded, A transistor 402 whose base is connected to the connection end of the transistor 401 and the capacitor 404, a base is connected to the collector of the transistor 402, and a collector is a connection end of the output end of the reset circuit 24 and the Reset terminal of the slave microcomputer 21 And a transistor 403 connected to the.

  The operation of the communication system using the delay circuit 23 shown in FIG. 4 will be described. Here, in order to simplify the description, an operation when a communication signal is transmitted from the main device microcomputer 11 to the sub device microcomputer 21 shown in FIG. 1 will be described. When the main apparatus microcomputer 11 of the main apparatus 10 shown in FIG. 1 does not communicate with the sub apparatus microcomputer 21, or when the main apparatus microcomputer 11 outputs the transmission data 1 to the sub apparatus microcomputer 21, the main apparatus The output level of the communication signal output from the Tx terminal of the microcomputer 11 for use is a high level. Accordingly, the transistor 401 illustrated in FIG. 4 is turned on, so that the capacitor 404 is charged and the transistor 402 is turned on. Accordingly, the base potential of the transistor 403 becomes a low level, and the transistor 403 is turned off. As a result, the input level of the Reset terminal of the slave device microcomputer 21 of the slave device 20 becomes the high level, and the reset is released.

  On the other hand, when the main unit microcomputer 11 of the main unit 10 shown in FIG. 1 outputs the transmission data 0 to the sub unit microcomputer 21, the output level of the communication signal output from the Tx terminal of the main unit microcomputer 11 is low level. It becomes. Accordingly, the transistor 401 illustrated in FIG. 4 is turned off. At this time, the electric charge stored in the capacitor 404 is discharged. Assuming that T1 is a period in which the transistor 402 can be kept on, that is, a period in which the charge stored in the capacitor 404 is discharged, the transistor 402 is kept on until the period T1 elapses. Therefore, until the period T1 elapses, the base potential of the transistor 403 is at a low level, and the transistor 403 is turned off. As a result, the input level of the Reset terminal of the slave device microcomputer 21 of the slave device 20 becomes the high level, and the reset is released.

  When the period during which the signal output of the transmission / reception signal synthesizing circuit 12 is at the low level is longer than the period T1, the charge stored in the capacitor 404 disappears when the period T1 elapses, so that the transistor 402 is turned off and the transistor 403 The base potential of the transistor 403 rises and the transistor 403 is turned on. The input level of the Reset terminal of the slave device microcomputer 21 becomes Low level, and the reset state is established. The operation of the delay circuit 23 does not hinder the operation of the reset circuit 24, and the reset state or reset release state of the slave device microcomputer 21 can be controlled only by the reset circuit 24.

  FIG. 5 is a diagram for explaining the relationship between the waveform of the communication signal output from the Tx terminal of the microcomputer for the main apparatus and the input level of the Reset terminal.

  (1) represents the waveform of the communication signal output from the Tx terminal of the microcomputer for the main apparatus. As described above, the output level of the communication signal output from the Tx terminal of the main device microcomputer 11 is determined when the main device microcomputer 11 does not communicate with the slave device microcomputer 21 or when the main device microcomputer 11 is not connected. When the transmission data 1 to the device microcomputer 21 is output, it is at a high level, and when the transmission data 0 to the slave device microcomputer 21 is output, it is at a low level. A pulse-like waveform indicated by symbol A represents transmission data transmitted from the main apparatus microcomputer 11 to the sub apparatus microcomputer 21. (2) represents the waveform of the communication signal input to the Rx terminal of the main unit microcomputer 11. In the illustrated example, two types of pulse-shaped waveforms are shown. One waveform represents transmission data transmitted from the Tx terminal of the main device microcomputer 11, and the other waveform indicated by reference character B represents transmission data as a slave device. It is a waveform of reply data returned from the slave device microcomputer 21 when it reaches the microcontroller 21. (3) represents the voltage level of the communication line 30 and the waveform of the communication signal transmitted to the communication line 30. (4) represents the input level of the Reset terminal of the slave device microcomputer 21.

  A period T1 is a time until the electric charge stored in the capacitor 404 is discharged. The period T2 is longer than the period T1, and is longer than the time during which the main device microcomputer 11 continues the low level, which is the output level when the transmission data 0 is output to the slave device microcomputer 21. The period T2 is set in the main device microcomputer 11. The period T3 is the time from when the reset of the slave device microcomputer 21 is released until the initialization of the slave device microcomputer 21 is completed.

  The operation of the communication system will be described in association with symbols A to G in the figure. (A) When transmission data is output from the Tx terminal of the microcomputer 11 for the main apparatus, and (B) when the transmission data reaches the microcomputer 21 for the slave apparatus, the slave microcomputer 21 transmits reply data to the transmission data. The reply data is transmitted to the Rx terminal of the main unit microcomputer 11. In the circuit configuration shown in FIG. 1, transmission data 1 output from the Tx terminal of the main device microcomputer 11 is also input to the Rx terminal of the main device microcomputer 11. Therefore, the transmission data 1 output from the Tx terminal of the main device microcomputer 11 and the reply data output from the sub device microcomputer 21 are input to the Rx terminal of the main device microcomputer 11. (C) At this time, the input level of the Reset terminal of the slave device microcomputer 21 is maintained at the high level by the delay circuit 23. Therefore, the slave device microcomputer 21 maintains the reset release state.

  (D) When any abnormality occurs in the slave device 20 and the reply data from the slave device microcomputer 21 is interrupted, (E) the master device microcomputer 11 switches the function of the Tx terminal from the communication output to the general-purpose output. . Further, the Low level is output from the TX terminal switched to the general-purpose output. That is, when it is determined that communication with the slave device microcomputer 21 is impossible, the main device microcomputer 11 outputs at a level different from the level at which communication is not performed in a state where communication is possible. In the illustrated example, when the main device microcomputer 11 does not communicate with the slave device microcomputer 21, or when the main device microcomputer 11 outputs the transmission data 1 to the slave device microcomputer 21, a high level is shown. To a different Low level. As a result, a low level signal is transmitted to the communication line 30. The main device microcomputer 11 maintains the signal output level at the Low level until the period T2 elapses. On the other hand, since the output level of the delay circuit 23 is high until the period T1 elapses, the input level of the Reset terminal of the slave device microcomputer 21 is high until the period T1 elapses. When the period T1 elapses, the output level of the delay circuit 23 becomes the Low level. That is, when the period T1 elapses, the reset signal is input to the Reset terminal of the slave device microcomputer 21, and the slave device microcomputer 21 is reset.

  (F) When the period T2 elapses, the main device microcomputer 11 switches the function of the Tx terminal of the main device microcomputer 11 from the general-purpose output to the communication output. By this switching, the output level of the Tx terminal becomes the output level when communication with the slave microcomputer 21 is not performed or the output level when the master microcomputer 11 outputs the transmission data 1 to the slave microcomputer 21. Switch. In the illustrated example, the output level of the communication signal output from the Tx terminal is switched from the Low level to the High level. As a result, a high level signal is transmitted to the communication line 30 and the reset of the slave device microcomputer 21 is released.

  (G) The master device microcomputer 11 waits until a period T3 from when the reset of the slave device microcomputer 21 is released until the initialization of the slave device microcomputer 21 is completed, and then transmits transmission data. To resume. (H) When the transmission data reaches the slave device microcomputer 21, the slave device microcomputer 21 resumes transmission of the reply data to the transmission data, and the reply data is transmitted to the Rx terminal of the master device microcomputer 11. .

  In the present embodiment, the configuration example of the communication system using the delay circuit 23 has been described. However, the communication system may be configured as follows. For example, an initialization signal determination unit is provided instead of the delay circuit 23, and the above-described period T1 is set in the initialization signal determination unit, and the initialization signal determination unit receives the initialization signal from the Tx terminal of the microcomputer 11 for main apparatus. When the main device microcomputer 11 does not communicate with the slave device microcomputer 21 or when the master device microcomputer 11 outputs the transmission data 1 to the slave device microcomputer 21, the duration time is different from the output level. Compared with the period T1, the input level of the Reset terminal is set to the High level until the duration of the initialization signal exceeds the period T1, and the input level of the Reset terminal is set when the duration of the initialization signal exceeds the period T1. Set to Low level. That is, when the period T1 has elapsed, the reset signal is input to the Reset terminal of the slave device microcomputer 21, and the slave device microcomputer 21 is reset. Even with this configuration, the same operation as that when the delay circuit 23 is used can be realized. Further, the existing reset circuit 24 is improved, for example, the input level of the Reset terminal is set to the High level until the initialization signal duration exceeds the period T1, and the Reset terminal when the initialization signal duration exceeds the period T1. The input level may be set to the Low level.

  In addition, although the transmission / reception signal combining circuit 12 and the transmission / reception signal combining circuit 22 are used in the communication system of the present embodiment, the configuration of the communication system is not limited to this, and the Tx terminal of the microcomputer 11 for the main apparatus The Rx terminal of the slave device microcomputer 21 may be connected by the communication line 30, and the Rx terminal of the master device microcomputer 11 and the Tx terminal of the slave device microcomputer 21 may be connected by the communication line 30.

  As described above, the communication system according to the present embodiment is a communication system in which a master device and a slave device transmit communication signals to each other via a communication line, and the master device is connected to the slave device. When it is determined that communication with the slave device is impossible due to the presence or absence of a reply from the slave device to the transmitted communication signal, the output level for transmitting the communication signal to the slave device is in a state where communication with the slave device is possible In this case, the slave device is switched to an output level different from the output level at the timing when communication is not performed, and the slave device resets the slave device when the output level switched by the master device continues for a predetermined time. With this configuration, it is possible to output a signal for resetting the slave device 20 at the Tx terminal which is a data transmission port in the master device 10. In the prior art disclosed in Patent Document 1 above, it is necessary to assign a dedicated port for outputting a reset signal in addition to the data transmission port to the microcomputer in the main unit. It has been difficult to reduce costs. On the other hand, in the communication system according to the present embodiment, there is no need to provide a dedicated port for outputting the reset signal, so that the cost associated with the configuration change for outputting the reset signal is unnecessary. In addition, since ports other than the data transmission port can be assigned to other uses, system resources can be effectively used without increasing costs.

  In addition, the master device according to the present embodiment includes a transmission / reception signal synthesis circuit that synthesizes a communication signal transmitted to the slave device and a communication signal transmitted from the slave device, and the slave device transmits to the master device. A transmission / reception signal combining circuit that combines a communication signal to be transmitted and a communication signal transmitted from the main apparatus. With this configuration, a transmission / reception signal between the main device and the slave device is also synthesized without providing a communication line for transmitting a reset signal, so a system is constructed with only one communication line 30. can do. Therefore, the cost associated with the installation of the communication line 30 can be reduced.

  In addition, the slave device according to the present embodiment includes a delay circuit that holds the output level switched by the master device for a certain time and outputs a reset signal that resets the slave device when the certain time has elapsed. With this configuration, the above effect can be obtained without modifying the slave device microcomputer 21 and the reset circuit 24.

  In the communication system according to the present embodiment, the communication line and the main device are insulated by a photocoupler, or the communication line and the main device are insulated by a photocoupler. As a result, for example, when the slave device is an operation unit that is frequently touched by the user, the power of the slave device can be supplied from a safe ground potential power source independent from the power source of the master device. Can increase the sex.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  10 main device, 11 microcomputer for main device, 12, 12A transmission / reception signal synthesis circuit, 20 slave device, 21 slave device microcomputer, 22 transmission / reception signal synthesis circuit, 23 delay circuit, 24 reset circuit, 30 communication line, 31 power line, 201, 202 Transistor, 301, 302 Photocoupler, 303 Transistor, 401, 402, 403 Transistor, 404 Capacitor.

Claims (6)

A communication system in which a master device and a slave device transmit communication signals to each other via a communication line,
When the master device determines that communication with the slave device is impossible due to the presence or absence of a reply from the slave device to the communication signal transmitted to the slave device, the output level for transmitting the communication signal to the slave device is Switch to an output level different from the output level at the timing when communication is not performed when communication with a slave device is possible,
The slave device resets the slave device when the output level switched by the master device continues for a predetermined time. The master device includes a transmission / reception signal combining circuit that combines a communication signal transmitted to the slave device and a communication signal transmitted from the slave device,
The communication system according to claim 1, wherein the slave device includes a transmission / reception signal combining circuit that combines a communication signal transmitted to the master device and a communication signal transmitted from the master device.   The slave device includes a delay circuit that holds the output level switched by the master device for a certain time and outputs a reset signal that resets the slave device when the certain time has elapsed. The communication system according to claim 1 or claim 2.   The master device sets an output level at a timing when communication is not performed when communication with the slave device is possible as a high level, and an output level when it is determined that communication with the slave device is impossible as a low level. The communication system according to any one of claims 1 to 3, wherein:   The communication system according to any one of claims 1 to 4, wherein the communication line and the main device are insulated by a photocoupler.   The communication system according to any one of claims 1 to 4, wherein the communication line and the slave device are insulated by a photocoupler.

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