JP6977623B2 - Communications system - Google Patents

Description

The present disclosure relates to a master-slave type communication system.

Conventionally, there is known a communication system provided with a plurality of devices such as a microcomputer and an ASIC, and configured to cooperate with each other by performing data communication between the plurality of devices.
In this type of communication system, for example, as described in Patent Document 1, a master microcomputer and a plurality of slave devices are connected via a common communication line, and the microcomputer is used as a chip select signal. It is configured to select a communication partner.

That is, in this communication system, as illustrated in FIG. 14, the output terminal SO and the input terminal SI for serial communication of the microcomputer 40 and the input terminal SI and the output terminal SO for serial communication of the plurality of devices 32 and 34. Is connected via a common communication line 4.

Further, the microcomputer 20 is provided with chip select terminals CS0 and CS1 corresponding to the devices 32 and 34. Then, the microcomputer 40 outputs a chip select signal from one of the chip select terminals CS0 and CS1 to the chip select terminal CS of the device 32 or 34 via the chip select signal line 2 for each device 32 and 34. Select the device to communicate with.

Further, the clock signal CLK is output from the microcomputer 40 to the devices 32 and 34 via the common clock signal line 6, and the devices 32 and 34 are connected to the devices 32 and 34 by the clock signal CLK input via the clock signal line 6. , Data is transmitted and received in synchronization with the microcomputer 40.

In the following description, the chip select signal is referred to as a CS signal, and the chip select signal line 2 used for transmitting the signal is referred to as a CS signal line 2.

Japanese Unexamined Patent Publication No. 2005-196486

By the way, in the above-mentioned conventional communication system, when the microcomputer 40 selects a device to be a communication partner, the output level of the target chip select terminal CS0 or CS1 is switched from an inactive level to an active level to obtain a CS signal. Is output.

Therefore, as shown by a cross in FIG. 14, when one of the CS signal lines 2 connected to the chip select terminals CS0 and CS1 of the microcomputer 40 is short-circuited and fixed at the active level, the data communication is normally performed. It may not be possible to carry out.

That is, when the CS signal line between the microcomputer 40 and the first device 32 is short-circuited and fixed at the active level, the microcomputer 40 selects the second device 34 and starts data communication. The device 32 of 1 erroneously recognizes the communication to itself. As a result, when the microcomputer 40 starts communication, not only the second device 34 but also the first device 32 transmits the response data.

In this case, if the response data from the first device 32 and the response data from the second device 34 are different, the response data interfere with each other on the communication line 4 for transmitting the response data, and the microcomputer 40 is abnormal. Data can be input, so that the microcomputer 40 can detect an abnormality.

However, for example, if the same response data is transmitted because the devices 32 and 34 are of the same type, the microcomputer 40 cannot detect the abnormality, and the microcomputer 40 communicates with the second device 34. Assuming that it is, normal communication will continue. As a result, the first device 32 in which the CS signal line is short-circuited may operate abnormally.

One aspect of the present disclosure is that in a master-slave type communication system, it is desirable to be able to promptly detect when the CS signal line used by the master communication unit to select a communication partner fails. ..

The communication system of one aspect of the present disclosure is a master-slave type communication system, and is a plurality of slave communication units (12, 14) having a communication function as a slave and a master communication unit (20) having a communication function as a master. ) And.

At the time of communication, the master communication unit outputs a chip select signal to one of a plurality of slave communication units via a chip select line (2) dedicated to each slave communication unit, so that the master communication unit becomes a communication partner. Select. Then, communication is performed with the selected slave communication unit via the communication line (4) common to each slave communication unit.

Further, a dedicated ID is assigned to each of the plurality of slave communication units. Then, each slave communication unit transmits its own ID via the communication line when communicating with the master communication unit. Further, the master communication unit compares the ID received via the communication line with the ID of the selected slave communication unit during communication with the selected slave communication unit, and determines an abnormality when the IDs do not match.

Therefore, when one of the CS signal lines connected to each slave communication unit is fixed to the active level due to a short circuit or the like, when the master communication unit selects the slave communication unit via the other CS signal line, the master communication unit is used. The abnormality will be detected promptly on the communication unit side.

That is, in this state, the ID is transmitted on the communication line from both the slave communication unit selected by the master communication unit and the slave communication unit whose CS signal line is fixed at the active level.

Since the ID is different for each slave communication unit, the communication signal of the ID interferes on the communication line, and abnormal data different from the ID of the selected slave communication unit is input to the master communication unit. To.

Therefore, by comparing the data with the ID of the selected slave communication unit, the master communication unit can promptly detect the occurrence of a communication abnormality and take measures against the abnormality such as communication stop.

Therefore, according to the communication system of the present disclosure, when the CS signal line is out of order, the communication abnormality cannot be detected, and the device on the slave communication unit side connected to the failed CS signal line operates abnormally. This can be suppressed and the reliability of the communication system can be improved.

In addition, the reference numerals in parentheses described in this column and the scope of claims indicate the correspondence with the specific means described in the embodiment described later as one embodiment, and the technical scope of the present invention is defined. It is not limited.

It is a block diagram which shows the structure of the communication system of 1st Embodiment. It is a time chart showing the communication operation between a microcomputer and a plurality of devices. It is a flowchart which shows the communication process executed by a microcomputer. It is a time chart which shows the communication operation at the time of short circuit of a CS signal line in a conventional communication system. It is a time chart which shows the communication operation at the time of short circuit of a CS signal line in an embodiment. It is explanatory drawing explaining the setting method of a device ID. It is a flowchart which shows the transmission / reception process which is executed by the microcomputer and the device of 2nd Embodiment. It is a time chart which shows the communication abnormality determination operation on the device side. It is a block diagram which shows the structure of the communication system of 3rd Embodiment. It is a time chart explaining the method of identifying an abnormal part in 3rd Embodiment. It is explanatory drawing explaining the operation when the microcomputer sets the ID of each device. It is explanatory drawing which shows the modification of the operation of FIG. It is a flowchart which shows the device ID setting process which is executed in the microcomputer and a device when the microcomputer sets the ID of each device. It is a block diagram which shows the structure of the conventional communication system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, in the communication system of the present embodiment, for example, in an electronic control device for vehicle control, a microcomputer 20 that performs various control processes is located between a plurality of devices 12 and 14 such as sensors and actuators. It is a communication system that performs master-slave communication.

The devices 12 and 14 correspond to the slave communication unit of the present disclosure, and are composed of ASIC0 and ASIC1 having a communication function as a slave in master-slave communication. Further, the microcomputer 20 corresponds to the master communication unit of the present disclosure, and has a communication function as a master in master-slave communication.

Therefore, the microcomputer 20 is provided with an output terminal SO for data transmission and an input terminal SI for data reception as communication terminals. The output terminal SO and the input terminal SI are connected to the input terminal SI and the output terminal SO, which are communication terminals of the devices 12 and 14, respectively, via a common communication line 4. The communication line 4 is composed of two communication lines, that is, a communication line for data transmission and a communication line for data reception when viewed from the microcomputer 20.

Further, the microcomputer 20 is provided with chip select terminals CS0 and CS1 corresponding to the devices 12 and 14. The chip select terminals CS0 and CS1 are connected to the chip select terminals CS of the devices 12 and 14 via dedicated CS signal lines 2 provided for the devices 12 and 14, respectively.

Further, the microcomputer 20 is also provided with a clock terminal CLK that outputs a clock signal to the devices 12 and 14 in order to synchronize with the devices 12 and 14. The clock terminal CLK is connected to the clock terminal CLK of each device 12 and 14 via a clock signal line 6 common to each device 12 and 14.

As shown in FIG. 2, the microcomputer 20 switches a CS signal to the CS signal line 2 by switching one of the chip select terminals CS0 and CS1 from a high level which is an inactive level to a low level which is an active level. Output and select the device to communicate with.

Then, during device selection, the microcomputer 20 transmits transmission data from the output terminal SO in synchronization with the clock signal. This transmission data is input to the input terminals SI of the devices 12 and 14, but the device to which the CS signal is not input discards the input data, so that the transmission data is a specific device selected by the CS signal. Received at 12 or 14.

Further, the specific device 12 or 14 selected by the CS signal transmits the response data from the output terminal SO in synchronization with the clock signal from the microcomputer 20, but the device not selected sends the output terminal SO. Keep open.

As a result, when viewed from the input terminal SI side of the microcomputer 20, the device not selected by the CS signal becomes high impedance, and the input terminal SI of the microcomputer 20 is the specific device 12 or 14 selected by the CS signal. The response data from will be input.

Therefore, the microcomputer 20 can select a device to be a communication partner and perform master-slave communication by switching one of the chip select terminals CS0 and CS1 from the inactive level to the active level.

Then, in order to carry out such communication, the microcomputer 20 is to output a CS signal from the chip select terminals CS0 and CS1 and to input / output transmission / reception data to the output terminal SO and the input terminal SI. Communication input / output unit 24 and a communication control unit 22 are provided.

The communication control unit 22 performs preset data communication with each of the devices 12 and 14 by a program executed by the CPU in the microcomputer 20. The communication control unit 22 is provided with a storage unit 26 in which a device ID table for specifying devices 12 and 14 to be communication partners is stored. The storage unit 26 is composed of a non-volatile memory.

The device ID table is data in which device names such as ASIC0 and ASIC1 and IDs that are unique identification information are set for each of the devices 12 and 14 with which the microcomputer 20 can communicate, and the communication control unit 22 is the device. The communication abnormality is determined using the ID table.

Therefore, each of the devices 12 and 14 is provided with storage units 13 and 15 in which their own IDs are stored, and each of the devices 12 and 14 stores its own ID in the transmission data at the time of communication with the microcomputer 20. It is configured to include. In the following description, the IDs given to the devices 12 and 14 are also referred to as device IDs.

Next, the communication process executed when the communication control unit 22 of the microcomputer 20 selects a device to be a communication partner and performs communication will be described.
As shown in FIG. 3, in this communication process, first, in S110, the device ID of the device 12 or 14 to be the communication partner is acquired from the device ID table stored in the storage unit 26.

Then, in the subsequent S120, the chip select terminal CS0 or CS1 corresponding to the device 12 or 14 as the communication partner is set to the active level, predetermined transmission data is transmitted from the output terminal SO, and reception data is acquired from the input terminal SI. , Perform send / receive processing.

In the transmission / reception process, when the transmission / reception of data is completed, the chip select terminal CS0 or CS1 set to the active level is returned to the inactive level.
Next, in S130, the device ID that may have been transmitted by the device 12 or 14 as the communication partner is extracted from the received data acquired in the transmission / reception processing in S120. Then, in the subsequent S140, the device ID of the communication destination acquired in S110 is compared with the device ID extracted in S130, and it is determined whether or not these device IDs match.

If it is determined in S140 that the device IDs match, the process proceeds to S150, the received data is the transmission data from the device 12 or 14 selected this time, and it is determined that the communication has ended normally. Then, the communication process is terminated.

On the other hand, if it is determined in S140 that the device IDs do not match, the device shifts to S160, and it is determined that some abnormality such as a short circuit of the CS signal line 2 has occurred, and the device selected this time is used. It stores or notifies that the communication of the above has failed, and ends the communication processing.

As described above, in the communication system of the present embodiment, a device ID unique to each device is set for each of the devices 12 and 14. Then, when the devices 12 and 14 are selected as communication partners by the CS signal from the microcomputer 20 and transmit / receive data to / from the microcomputer 20, their own device ID is included in the transmission data.

On the other hand, when the microcomputer 20 sets the chip select terminal CS0 or CS1 to the active level, selects the device 12 or 14 as the communication destination device, and transmits / receives data to / from the selected device, the communication destination device is transmitted from the received data. Get the device ID of. Then, when the acquired device ID does not match the device ID of the communication destination device stored in the storage unit 26, it is determined that an abnormality has occurred in the communication, and a notification to that effect is given.

Therefore, according to the communication system of the present embodiment, when the CS signal line 2 of another device different from the communication destination device selected by the microcomputer 20 as the communication partner is short-circuited and fixed at the active level, the microcomputer Communication abnormalities can be quickly detected on the 20 side.

Further, since the microcomputer 20 can take measures against an abnormality such as a communication stop by storing or outputting the detection of a communication abnormality, the communication is continued in the abnormal state, and the devices 12 and 14 become abnormal. It can be suppressed from operating.

Therefore, according to the communication system of the present embodiment, the reliability can be improved as compared with the conventional communication system shown in FIG.
That is, in the conventional communication system shown in FIG. 14, although the devices 32 and 34 may be given an ID indicating the type of the device, the devices 32 and 34 of the same type are given a unique ID. There is no such thing.

Therefore, even if the device IDs are assigned to the response data when the devices 32 and 34 transmit the response data to the microcomputer 40, when the devices 32 and 34 respond at the same time, the microcomputer 40 On the side, it is not possible to determine the abnormality from the device ID.

That is, as shown in FIG. 4, when the microcomputer 40 selects the device 34 and starts communication in a state where the CS signal line of the device 32 is short-circuited and fixed at the active level, the devices 32 and 34 are displayed. Send response data containing the same device ID.

Therefore, in this case, when the devices 32 and 34 transmit the response data having different contents, the microcomputer 40 can detect the communication abnormality by performing the error determination of the response data by a well-known parity check or the like.

However, when the respective devices 32 and 34 transmit the response data having the same contents, the transmitted data from the respective devices 32 and 34 all match, so that the communication abnormality cannot be detected on the microcomputer 40 side. ..

On the other hand, in the present embodiment, as shown in FIG. 5, when the microcomputer 20 selects the other device 14 in a state where the CS signal line of the device 12 is short-circuited and fixed at the active level, each device is used. 12 and 14 transmit response data including a unique device ID.

Therefore, even if the devices 12 and 14 transmit the same response data, the microcomputer 20 can detect the communication abnormality based on the device ID extracted from the received data.
That is, as shown in FIG. 5, when the device ID of ASIC0 constituting the device 12 is "000001" and the device ID of ASIC1 constituting the device 14 is "0000010", the devices 12 and 14 respond. Suppose you have sent data.

In this case, high / low binary signals corresponding to the device IDs of the devices 12 and 14 are combined and input to the input terminal SI of the microcomputer 20, and the level of the input terminal SI is the lower two bits of the device ID. In the region of, the potential is between high and low.

Therefore, on the microcomputer 20 side, the device ID assigned to the received data is recognized as "000000" or "0000011" depending on the potential.
Since the device ID recognized in this way is different from the device ID "0000010" that should be originally received, the microcomputer 20 side communicates from the device ID regardless of the content of the response data from the devices 12 and 14. You will be able to detect abnormalities.

Further, even if the CS signal line is normal, even if there is an abnormality in the communication operation of the selected device, or if disturbance noise is superimposed on the communication line 4 and a communication failure occurs, the microcomputer is used during communication. The device ID input to 20 will be different from the device ID that should be originally received.

Therefore, according to the communication system of the present embodiment, various communication abnormalities can be detected by confirming the device IDs transmitted from the devices 12 and 14 that function as slave communication units on the microcomputer 20 side that functions as the master communication unit. Can be detected.

Therefore, according to the present embodiment, the reliability can be improved as compared with the conventional communication system.
Here, in the present embodiment, the device ID of the ASIC 0 constituting the device 12 is set to "000001", and the device ID of the ASIC 1 constituting the device 14 is set to "000001".

This is because when the device IDs output in synchronization with the clock signals from the devices 12 and 14 interfere with each other on the communication line 4, the device 12 or 14 is on the microcomputer 20 side from the potential of the input terminal SI of the microcomputer 20. This is to prevent it from being recognized as the device ID of.

That is, for example, as shown in the upper part of FIG. 6, in a state where the ID of ASIC0 is set to "000000" and the ID of ASIC1 is set to "000111", the device IDs communicate with each other from the devices 12 and 14 at the same time. It is assumed that the output is on the line 4.

In this case, although the lower 3 bits of the two device IDs are different, when they are transmitted to the communication line 4 at the same time, the lower 3 bits interfere with each other, so that the potential of the input terminal SI of the microcomputer 20 is low corresponding to the value 0. It is an intermediate potential between the level: 0V and the high level: 5V corresponding to the value 1.

Then, the microcomputer 20 identifies whether the input data is "0" or "1" by comparing the intermediate potential with the threshold value, and identifies the received device ID. Therefore, the device ID is the device ID. It will be recognized as "000111" or "000000".

Therefore, when the device ID is set as described above, when the two devices 12 and 14 simultaneously transmit the response data due to a short circuit of the CS signal line 2, the device ID extracted from the received data on the microcomputer 20 side communicates. It may match the device ID of the destination device.

Therefore, in the present embodiment, when the device IDs are simultaneously transmitted from the devices 12 and 14 and interfere with each other on the communication line, the microcomputer 20 side does not recognize the device ID as the device ID of the communication destination device. The device ID is set.

Specifically, in the present embodiment, among the 6-bit digital data constituting the device IDs of the devices 12 and 14, the lower 2 bits are complementarily set as "01" and "10" to be higher. The 4 bits are set to the same value "0000".

Therefore, even if the device IDs are simultaneously transmitted from the devices 12 and 14, the lower 2 bits of the device ID extracted from the received data on the microcomputer 20 side are "00" or "11".

Therefore, in the communication process, the microcomputer 20 can accurately determine the communication abnormality by comparing the device ID extracted from the received data with the device ID of the communication destination device.

The device ID does not necessarily have to be set as described above, and each device ID is digital data of a predetermined bit, includes bit values of a value 1 and a value 0, and is at least between the two device IDs. It suffices if some bit values are set so as to be complementary so as to be different.

Further, in this case, the n / 2 bit values of the n-bit digital data constituting each device ID may be set to be different from each other.
That is, for example, as shown in the lower part of FIG. 8, each device ID may be set as “000111” and “111000” in a complementary manner. Further, the two device IDs may be complementarily set as, for example, "101001" and "010110".

Then, in this way, the device ID recognized by the microcomputer side when the two device IDs interfere with each other becomes "000000" or "111111", and the bit value of 1/2 of the n-bit data is the communication destination device. It will be different from the device ID of.

Therefore, in this case, even if a part of the bit value that is assumed to be different from the device ID of the communication destination device matches the bit value of the device ID due to noise or the like, the communication abnormality can be detected. The accuracy of detecting communication abnormalities can be further improved.
[Second Embodiment]
In the first embodiment, the microcomputer 20 as the master communication unit determines the communication abnormality based on the device ID included in the response data transmitted from the devices 12 and 14 as the slave communication unit.

On the other hand, in the present embodiment, when the microcomputer 20 transmits various command data to the device 12 or 14 which is the communication partner, the device ID is included in the transmission data, so that the devices 12 and 14 also communicate with each other. Allows you to detect anomalies.

The device configuration and operation of this embodiment are basically the same as those of the first embodiment, and the differences from the first embodiment are the transmission / reception processing of S120 executed by the communication control unit 22 of the microcomputer 20 and the transmission / reception processing thereof. This is a transmission / reception process executed on the devices 12 and 14 in response to the above.

Therefore, in the present embodiment, the transmission / reception processing executed by the communication control unit 22 of the microcomputer 20 and the devices 12 and 14 will be described.
As shown in FIG. 7, when the communication control unit 22 of the microcomputer 20 performs transmission / reception processing in S120 of FIG. 3, first, in S210, the communication destination is set to the command ID indicating the command content for the communication destination device. Generates and transmits transmission data with the device ID of the device.

Then, after the data is transmitted, the process proceeds to S220 to execute a reception process for receiving the response data representing the control result for the transmitted command from the communication destination device, and the transmission / reception process is terminated.

The microcomputer 20 sets the chip select terminal CS0 or CS1 corresponding to the communication destination device to the active level when transmitting command data in S210 or acquiring response data from the communication destination device in S220, and CS. Output a signal.

On the other hand, each of the devices 12 and 14 executes the transmission / reception processing shown in FIG. 7 when the chip select terminal CS is at the active level.
In this transmission / reception processing, first, the reception processing for receiving the transmission data from the microcomputer 20 is performed in S310, and then in S320, the device ID is extracted from the reception data obtained in the reception processing.

Next, in S330, the device ID extracted in S320 is compared with its own device ID stored in the storage unit 13 or 15, and it is determined whether or not these device IDs match.

When it is determined in S330 that the device IDs match, the received data received this time is a command transmitted to itself, so in S340, a predetermined control corresponding to the command is performed. Is executed, and the process proceeds to S360.

Then, in S360, the transmission process of transmitting the response data indicating that the control is normally executed is performed to the microcomputer 20, and the transmission / reception process is terminated.
On the other hand, if it is determined in S330 that the device IDs do not match, the received data received this time is not a command transmitted to itself, so a communication error occurs in S350. It is determined that there is, and the preset fail-safe process is executed.

The fail-safe process includes, for example, an output stop process for stopping the output of the detection result by the sensor and the output of the drive signal to the actuator, a degeneration control process for safely stopping the vehicle, and the like. can.

Then, when the fail-safe process is performed in S350, the process proceeds to S360 and the transmission / reception process is terminated.
As described above, in the present embodiment, the microcomputer 20 is the device 12 or 14 as the communication partner.
When sending a command to, generate transmission data including the device ID of the corresponding device.

Then, each of the devices 12 and 14 determines whether or not the device ID included in the transmission data from the microcomputer 20 matches its own device ID, and if they do not match, a communication error occurs. Assuming that it is, a predetermined fail-safe process is carried out.

Therefore, for example, as shown in FIG. 8, when the microcomputer 20 selects the device 12 and transmits a command in a state where the CS signal line of the device 12 is short-circuited and fixed at the active level, the device is used. 12 will operate in response to the command.

On the other hand, when the microcomputer 20 selects the device 14 and transmits a command to the device 14, the command is received by both the devices 12 and 14. Since the device ID of the device 14 selected by the microcomputer 20 is given to the command, the device 14 can operate normally in response to the command from the microcomputer 20.

On the other hand, since the device ID given to the command is different from its own device ID, the device 12 determines that a communication abnormality has occurred and performs a predetermined fail-safe process.

Therefore, according to the present embodiment, the device in which the communication abnormality has occurred can be separated from the control system, and the stop / degeneracy control can be safely performed.
[Third Embodiment]
The communication system of this embodiment basically has the same configuration as that of the first embodiment, and is different from the first embodiment in that the number of devices connected to the microcomputer 20 is three. be.

Therefore, as shown in FIG. 9, the microcomputer 20 outputs a CS signal to the chip select terminal CS of the third device 16 having a communication function as a slave via the CS signal line 2 dedicated to the device 16. The chip select terminal CS2 for this purpose is provided.

The device 16 is composed of the ASIC 2 like the other devices 12 and 14, and has a built-in storage unit 17 in which its own device ID is stored.
Further, the output terminal SO and the input terminal SI for communication of the device 16 are connected to the microcomputer 20 via the communication line 4 common to the other devices 12 and 14, and the clock terminal CLK is also connected to the other devices 12 and 14. It is connected to the microcomputer 20 via a common clock signal line 6.

The device IDs of the three devices 12, 14, and 16 each include a bit value of a value 1 and a value 0 in the n-bit data, and some bit values are the other two device IDs. It is set complementarily so that the bit value is different from that of.

Specifically, the device ID of the device 12 is set to "101001", the device ID of the device 14 is set to "100110", and the device ID of the device 16 is set to "011010".

Therefore, in the present embodiment, even if the device IDs are output from the three devices 12, 14, and 16 at the same time, the microcomputer 20 can detect the communication abnormality by the same procedure as in the first embodiment.

Further, in each of the above device IDs, a bit area of n-bit data is divided by the number of devices: 3, each divided area is assigned to each device ID, and the bit value is another in the assigned specific area. It is complementarily set so that it has a unique value different from the device ID.

That is, in the device ID of the device 12, the lower 2 bits of all 6 bits are set to "01", which is different from the bit value "10" of the other device ID. Similarly, the device ID of the device 14 is set to "01" in which the central 2 bits are different from the other device IDs, and the device ID of the device 16 is set to "01" in which the upper 2 bits are different from the other device IDs. Has been done.

As a result, in the communication system of the present embodiment, by performing the above-mentioned communication processing by the microcomputer 20, not only the communication abnormality can be detected, but also the abnormal portion causing the communication abnormality can be easily identified.

That is, when the number of devices is two as in the first embodiment, when the device ID is transmitted from the communication destination device and another device at the time of communication with the communication destination device, and the microcomputer 20 determines the communication abnormality. It is conceivable that the CS signal line 2 of another device is short-circuited.

On the other hand, when the number of devices is three as in the present embodiment, when the microcomputer 20 determines a communication abnormality, the cause of the abnormality is considered to be the CS signal line 2 of the other two devices. It is not possible to specify which of the two CS signal lines 2 is short-circuited.

For example, as shown in FIG. 10, when the microcomputer 20 selects the device 14 in a state where the CS signal line 2 of the device 12 is short-circuited and fixed at the active level, the devices 12 and 14 are unique. The response data including the device ID is transmitted.

In this case, the microcomputer 20 can detect a communication abnormality by extracting the device ID from the received data and comparing it with the device ID of the device 14.
However, it is specified whether the cause of the communication abnormality is a short circuit of the CS signal line 2 of the device 12 or a short circuit of the CS signal line 2 of the device 16 only by comparing the device IDs. Can't be done.

Therefore, in order to identify the short circuit of the CS signal line 2 of the device 12 only by comparing the device IDs, the microcomputer 20 needs to select the device 16 and perform communication.
That is, as shown in "Abnormality location identification method 1" of FIG. 10, if the microcomputer 20 detects a communication abnormality during communication with the device 14, then selects the device 16 and starts communication, the device Since 12 and 16 transmit the response data, the communication abnormality is detected again.

Therefore, on the microcomputer 20 side, by detecting the communication abnormality twice, when communicating with the device 14 and when communicating with the device 16, the cause of the communication abnormality is considered to be the CS signal line 2 of the device 12. It can be specified that it is a short circuit of.

However, in order to identify the abnormal portion in this way, it is necessary for the microcomputer 20 to change the communication destination device and perform communication a plurality of times, which takes time. It is also possible that the device will malfunction due to multiple communications.

On the other hand, in the present embodiment, the device IDs of the devices 12, 14 and 16 divide the bit area of the 6-bit data into three and allocate them as a specific area of each device ID, and the bit value of the specific area is another. It is set to be "01" which is different from the device ID of.

Therefore, as shown in "Abnormality location identification method 2" of FIG. 10, the microcomputer 20 compares the device ID extracted from the received data at the time of communication with the device 14 with the device ID of the device 14 to obtain an abnormality. It is possible to identify the short-circuited portion of the CS signal line 2 which is considered to be the cause.

That is, the microcomputer 20 identifies a bit different from the legitimate device ID that should be originally received in the device ID extracted from the received data.
Since the bits are a bit in a specific area of the device being communicated and a bit in a specific area of the device in which the CS signal line 2 is at the active level, the device considered to have the CS signal line 2 short-circuited. Can be identified as the device 12.

Therefore, according to the present embodiment, in the process of S160 shown in FIG. 3, the microcomputer 20 communicates with one of the devices by specifying the short-circuited portion of the CS signal line 2 by such a procedure, and a communication abnormality occurs. At the same time, it becomes possible to identify the abnormal part.

Therefore, it is not necessary to communicate with a plurality of devices in order to identify the abnormal portion, and it is possible to suppress the device from malfunctioning due to the plurality of communications.
[Fourth Embodiment]
In the above embodiment, it has been described that the device ID unique to each device is stored in the storage unit of each device in advance, but the device ID may be written to the storage unit of each device at the time of manufacture. , The microcomputer 20 may carry out after constructing the communication system.

When the microcomputer 20 writes the device ID after the communication system is constructed, it is not necessary to create the device ID table and write the device ID to the storage unit 26 of the communication system 20 at the time of constructing the communication system. The system can be easily constructed.

Therefore, next, as the fourth embodiment of the present disclosure, the operation when the microcomputer 20 writes the device ID to the storage units 13 and 15 of the devices 12 and 14 in the communication system of the first embodiment will be described.

First, in order for the microcomputer 20 to write the device ID after the construction of the communication system, the storage units 13 and 15 of the devices 12 and 14 are each configured with a memory in which data such as the device ID can be rewritten. ..

Then, when setting the device IDs of the devices 12 and 14, the microcomputer 20 sequentially selects the communication destination device by the CS signal as shown in FIG. 11, and the selected device 12 or 14 is used. , Send the device ID setting command.

On the other hand, when each of the devices 12 and 14 receives the device ID setting command while being selected as the communication partner by the CS signal from the microcomputer 20, the device ID assigned to the setting command is extracted. , Write to its own storage units 13 and 15.

By doing so, in each of the devices 12 and 14, the device ID stored in the storage units 13 and 15 is changed from, for example, “000000” at the time of shipment to the device IDs “0000001” and “000001” unique to each device 12 and 14. Will be rewritten as.

Therefore, after setting the device IDs of the devices 12 and 14 in the above procedure, the microcomputer 20 communicates with the devices 12 and 14 by performing the communication process of FIG. 3, and the devices 12 and 14 are communicated with each other. Communication abnormality can be detected based on the device ID transmitted from 14.

By the way, when the microcomputer 20 sets the device IDs of the devices 12 and 14, if one of the devices 12 and 14 has a short-circuited CS signal line 2 and is fixed at the active level, the device is fixed to the active level. , The device ID of the other device may be set.

Therefore, as shown in FIG. 12, when the devices 12 and 14 receive the device ID setting command from the microcomputer 20 and rewrite the device ID in the storage units 13 and 15, the device ID before rewriting is used as the response data. It may be transmitted to the microcomputer 20.

By doing so, the microcomputer 20 side extracts the device ID from the response data and determines whether or not the extracted device ID is the device ID before rewriting, so that the device ID can be written normally. You will be able to judge whether it was possible or failed.

Then, for this purpose, the device ID setting process shown in FIG. 13 may be executed in the microcomputer 20 and the devices 12 and 14, respectively.
That is, the microcomputer 20 starts the device ID setting process shown in FIG. 13 at the time of initial setting immediately after the construction of the communication system or when the setting condition of the device ID is satisfied.

Then, the microcomputer 20 first acquires the device ID of the device 12 or 14 for which the device ID is set in S410 from the device ID table stored in the storage unit 26, and shifts to S420.

In S420, the chip select terminal CS0 or CS1 connected to the device 12 or 14 corresponding to the device ID acquired in S410 is set to the active level, and the device ID setting command including the device ID acquired in S410 is issued from the output terminal SO. Send.

On the other hand, each of the devices 12 and 14 executes the device ID setting process shown in FIG. 13 when the device ID is not set or when the device ID setting condition is satisfied.
Then, each of the devices 12 and 14 first determines in S510 whether the device ID setting command has been received via the input terminal SI, and then waits for the device ID setting command to be received.

When it is determined in 510 that the device ID setting command has been received, the process proceeds to S520, the device ID before rewriting is read from its own storage unit 13 or 15, and response data including this device ID is generated. The data is transmitted from the output terminal SO to the microcomputer 20.

Then, in the subsequent S530, the device ID is extracted from the received device ID setting command, the device ID stored in the own storage unit 13 or 15 is rewritten, and the device ID setting process is terminated.

On the other hand, when the device ID setting command is transmitted in S420, the microcomputer 20 transmits the response data before rewriting from the devices 12 and 14, so the process shifts to S430 and the response data is received via the input terminal SI. do.

Then, in the following S440, the device ID is extracted from the received response data, transferred to S450, and the device ID extracted in S440 and the device 12 or 14 to which the device ID setting command is transmitted in S420 are not rewritten. Compare with device ID.

In S460, as a result of the comparison in S450, it is determined whether or not the device ID extracted from the response data and the device ID before rewriting match.
Then, if the device IDs match, it is determined that the device ID rewriting was successful, the process proceeds to S470, the device ID rewriting is successfully stored or notified, and the communication process is terminated. ..

If the device IDs do not match, it is determined that the rewriting of the device ID has failed, the process proceeds to S480, the memory or notification that the rewriting of the device ID has failed is stored or notified, and the communication process is terminated. ..

By executing the device ID setting process in this way, the device ID can be set while confirming that the device IDs of the devices 12 and 14 have been correctly rewritten, and the reliability at the time of setting the device ID is improved. can.

Although the embodiment for carrying out the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment, and can be variously modified and carried out.
For example, in the above embodiment, the communication system has been described as being composed of a microcomputer 20 that performs various control processes in an electronic control device for vehicle control, and a plurality of devices 12 and 14 such as sensors and actuators.

However, the technique of the present disclosure is a communication system in which a device having a function as a master communication unit and a plurality of devices having a function as a slave communication unit perform data communication using a common communication line. , The same as the above embodiment can be applied.

Therefore, all the devices serving as the master communication unit and the slave communication unit may be configured by a microcomputer or an electronic circuit such as an ASIC, and may be configured by a combination of these. May be good.

A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or one function possessed by one component may be realized by a plurality of components. Further, a plurality of functions possessed by the plurality of components may be realized by one component, or one function realized by the plurality of components may be realized by one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other above embodiment. It should be noted that all aspects included in the technical idea specified only by the wording described in the claims are embodiments of the present invention.

2 ... CS signal line, 4 ... Communication line, 6 ... Clock signal line, 12, 14, 16 ... Device, 13, 15, 17 ... Storage unit, 20 ... Microcomputer, 22 ... Communication control unit, 24 ... Communication input / output unit , 26 ... Memory.

Claims (4)

A plurality of slave communication units (12, 14, 16) having a communication function as a slave in master-slave communication, and
It has a communication function as a master in the master-slave communication, and when communicating with one of the plurality of slave communication units, one of the plurality of slave communication units is a chip select line dedicated to each slave communication unit. By outputting the chip select signal via (2), a slave communication unit to be a communication partner is selected, and a communication line (4) common to each slave communication unit is connected to the selected slave communication unit. With the master communication unit (20), which communicates via
Equipped with
A dedicated ID is assigned to each of the plurality of slave communication units.
Each of the slave communication units transmits its own ID via the communication line when communicating with the master communication unit.
When communicating with the selected slave communication unit, the master communication unit compares the ID received via the communication line with the ID of the selected slave communication unit, and if the IDs do not match, an abnormality occurs. It is structured to judge,
Further, the plurality of slave communication units are configured so that the ID can be rewritten by a command from the master communication unit.
When the master communication unit transmits the ID rewriting command to the slave communication unit to be rewritten, the master communication unit acquires the ID before rewriting transmitted from the slave communication unit, and the ID is the ID. When it matches the ID before rewriting recognized by the master communication unit side, it is determined that the ID has been correctly rewritten by the rewriting command.
A communication system that is configured to. When communicating with the selected slave communication unit, the master communication unit transmits the ID of the slave communication unit via the communication line.
When the chip select signal is input via the dedicated chip select line, each slave communication unit compares the ID received via the communication line with its own ID, and when the IDs do not match. To judge the abnormality,
The communication system according to claim 1, which is configured as such. When the ID of each slave communication unit is transmitted to the master communication unit at the same time as the ID of the other slave communication unit, the master communication unit side recognizes the ID of the selected slave communication unit. The communication system according to claim 1 or 2, which is set so as not to be present. The ID of each slave communication unit is digital data of a predetermined bit, and is a specific area assigned to each slave communication unit by dividing the bit area of the digital data by the number of each slave communication unit, and is another slave communication unit. The communication system according to claim 3, wherein the communication system is set to have a unique value different from that of the third.

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