JP4244844B2 - Serial communication method and communication apparatus - Google Patents

Description

  The present invention relates to a serial communication method and a communication apparatus for transmitting / receiving serial data via a communication line.

  Conventionally, as a serial communication system configured such that a plurality of communication devices connected via a communication line can transmit and receive serial data to each other, for example, a plurality of electronic control devices (hereinafter referred to as “ECUs”) mounted on a vehicle. There are known in-vehicle serial communication systems configured to control each part of a vehicle by performing data communication with each other.

  An example of a communication format in this in-vehicle serial communication system is shown in FIG. FIG. 16 shows a communication format of general asynchronous serial communication, and one frame is composed of a plurality of bytes of data. For example, when one ECU sends out the data for one frame on the communication line, the other ECUs receive it. At this time, the communication line continues for a predetermined bit (for example, 10 bits) or more. When a high level (hereinafter referred to as “H level”) state is reached, it is detected that the transmission of one frame of data from the transmission source ECU has ended, that is, the communication line has entered an idle state. .

  When the idle state is detected, each ECU performs a predetermined process based on the received data. Then, when there is an ECU that should make some response, the ECU sends the data to be sent to the communication line in the same format as described above.

  In addition, as shown in FIG. 16, each 1-byte data constituting one frame is added to the head of NRZ (non-return zero) type effective data consisting of 8 bits from bit 0 to bit 7 and the head thereof. Are composed of a low-level start bit (hereinafter referred to as “L-level”) and an H-level stop bit added to the end thereof.

  By the way, each ECU constituting this type of serial communication system includes a microcomputer (hereinafter referred to as “microcomputer”) in order to control the serial communication operation and operations other than the communication of the ECU. As such a microcomputer, one having hardware for detecting the above-described idle state is known (for example, see Non-Patent Document 1).

  FIG. 17 shows an example of a microcomputer configured to perform hardware detection of an idle state. As shown in the figure, the microcomputer 100 includes a ROM 102 for storing a program, a CPU 101 for executing the program stored in the ROM 102, a RAM 103 for temporarily storing calculation results by the CPU 101, and serial data on the communication line L1 as a reception buffer 107. And a communication unit 104 that receives serial data via the data input port P2 and transmits serial data onto the communication line L1 via the data output port P1 and the transmission buffer 106. In the following description, data input to the data input port P2 via the reception buffer 107 is received data RxD, and data transmitted from the communication unit 104 to the transmission buffer 106 via the data output port P1 is transmitted data TxD. That's it.

The communication unit 104 includes an idle detection unit 108 that detects an idle state based on the reception data RxD input to the data input port P2. The idle detection unit 108 is hardware originally provided in the microcomputer 100. Therefore, a user who uses the microcomputer 100 can set up a serial communication control program using the detection result of the idle detection unit 108.
“MCCI Reference Manual (Multichannel Communication Interface Reference Manual)”, Rev. 1 (Rev. 1.0), p. 68-69, 72, 75, [online], Motorola Incorporated, [searched on March 29, 2004], Internet <URL: http://e-www.motorola.com/files/ microcontrollers / doc / ref_manual / MCCIRM.pdf>

  However, the microcomputer that controls the serial communication is not necessarily configured to detect the idle state in hardware like the microcomputer 100, and there is a microcomputer that does not include such hardware.

  If you want to perform serial communication and other various controls using a microcomputer that does not have hardware that detects such an idle state, the microcomputer cannot detect the idle state in the same (default) state, and data , That is, the end of reception of one frame described with reference to FIG. 16 cannot be determined. For this reason, there is a case where a communication error occurs and communication cannot be performed even though normal communication is performed.

  The present invention has been made in view of the above problems, and an object of the present invention is to enable normal serial communication by detecting an idle state of a communication line when performing serial communication between a plurality of communication devices.

The invention of claim 1, wherein has been made to solve the above problems, I serial communication method der for transmitting and receiving serial data between a plurality of communication devices connected via the communication line each other, the communication apparatus, After the start of serial data reception, it is determined at every predetermined timing whether or not an edge of the received data has been detected before a predetermined determination time elapses from that timing. When the edge is not detected before the determination time elapses, and the logical level of the communication line at the determination time elapses is not the active level, the communication line is in the idle state. Judge that there is.

That is, if an edge is detected during the determination time, it is considered that the unit data has been received at least during the determination time, but there is no edge change in the idle state (for example, H Therefore, if no edge is detected during the determination time, it is determined to be in an idle state .
However, even when an edge is not detected during the determination time, for example, it may be considered that only bit data of an active level is continuously received during the determination time. In such a case, an edge is not detected during the reception of data.
Therefore, in the present invention (Claim 1), when the edge is not detected before the determination time elapses and the logical level of the communication line at the time of the determination time elapses is not the active level. The idle state is determined.

Therefore, according to the above method, the idle state of the communication line is detected in order to determine the presence / absence of an edge during the determination time at each predetermined timing, and to determine whether the state is the idle state based on the determination result. Thus, normal serial communication can be performed.
In addition, even if an edge is not detected due to continuous reception of only a plurality of bits whose logical level is the active level during the determination time, the idle state is not determined based on the logical level. It becomes possible to carry out more accurately.

  The edge to be detected may be, for example, either a rising edge or a falling edge, or both rising and falling edges. Where is the format of each bit constituting the unit data and the timing described above? It may be determined appropriately in consideration of the above. In addition, the determination time may be set as appropriate according to the data format, for example, to be long enough to receive several bits of unit data during the determination time. The timing may be set as appropriate as long as it can be appropriately determined whether or not it is in an idle state, for example, every time reception of unit data ends.

Here, for example, in the serial communication method according to claim 1 , when the timing is, for example, at the end of reception of unit data, an edge occurs between the end of the reception and the elapse of the determination time depending on the communication speed. Even if it cannot be detected, it may be possible. That is, for example, when it is configured to start edge detection within the determination time by reception interrupt processing at the end of unit data reception, the reception interrupt processing may not be started at the same time as reception end, but from the end of reception It is also conceivable that the reception interrupt process is started after a predetermined period. In such a case, if the reception interrupt process is started after several bits of the next unit data have already been received due to the high communication speed, an edge occurs in the received several bits. If it does, it will not be detected.

Therefore, in order to accurately detect the idle state regardless of the communication speed, for example, the serial communication method according to claim 2 may be used. That is, in the serial communication method according to claim 2 , the serial data is configured as a data frame including a plurality of unit data, with the data having a predetermined number of bits as unit data, and the communication device detects an edge of the received data. The detection time is stored every time. Each time the unit data is received, the reception of the unit data is performed based on the detection time of the edge detected immediately before the end of the reception and the number of received bits from the edge to the end of the reception of the unit data. Calculate the end time.

  Then, a time obtained by adding at least the data gap time and the time corresponding to the data length of the unit data to the reception end time is set as an idle determination time, and unit data is set between the reception end time and the idle determination time. If not received, it is determined that the communication line is idle. Here, the data gap time is the time from the end of reception of unit data to the start of reception of the next unit data.

  That is, since the data length (time) per bit is known in advance, if the edge detection time during unit data reception is stored, the bits from that edge to the end of the unit data reception are stored at that edge detection time. By adding a time corresponding to the number, the reception end time of the unit data can be accurately calculated. Then, if the time corresponding to the data gap time and the data length of one unit data is further added to the calculated reception end time, the reception end time of the next unit data is accurately calculated. The time is set as the idle determination time.

That is, instead of looking at the presence or absence of an edge within a certain period (determination time) as in the method of claim 1 , an idle determination time corresponding to the reception end time of the unit data and the reception end time of the next unit data Are accurately calculated, and whether or not unit data is received between the two times is determined. Both times are accurately calculated regardless of the communication speed.

  Therefore, according to the above method, each time related to the idle determination is accurately calculated, and the determination of the idle state is performed based on each calculated time. Therefore, even if the communication speed becomes high, the determination Can be done accurately.

  Note that the data gap time depends on the serial communication format, for example, when it is a time of several bits, or when it is zero (that is, when a plurality of unit data are continuously transmitted and received without any interval). There are various possibilities.

Next, the invention described in claim 3 is a communication device that is connected to a communication partner device via a communication line and can transmit / receive serial data to / from each other, and detects an edge of data received via the communication line. Edge detection means is provided.

This is a case where the edge determining means operates at a predetermined timing after the start of serial data reception and no edge is detected by the edge detecting means until a predetermined determination time elapses from the timing. In addition, when the logical level of the communication line when the determination time has elapsed is not the active level, it is determined that the communication line is in an idle state.

According to the communication apparatus configured in this way, it is determined whether or not the idle state is based on the presence or absence of edge detection during the determination time, and, for example, only the bits of the active level are continued during the determination time. even but not detected, since no erroneous determination that erroneously it idle, the serial communication method according to claim 1, wherein is realized, similarly to claim 1, successfully detecting the idle state of the communication line Serial communication can be performed. For example, for a microcomputer that does not have hardware for determining an idle state but has an edge detection means, the microcomputer is caused to execute a program for causing the microcomputer to function as an idle determination means. Can be performed in software.

More specifically, the communication device according to the third aspect can be configured as described in the fourth aspect, for example. That is, a timing means for measuring the determination time, and a detection state holding means for holding information indicating that the edge is detected when the edge is detected by the edge detection means, the idle determination The means includes a timing start unit, a detection state initialization unit, an edge determination unit, and a level determination unit.

  The timing start unit starts counting the determination time by the timing unit at each timing, and the detection state initialization unit initializes the detection state holding unit at each timing. Then, the edge determination unit determines whether or not an edge is detected during the determination time based on information held in the detection state holding unit when the timing by the timing unit is completed. The level determination unit determines the logical level of the communication line at the time when the time measuring means ends.

  Note that when edge detection is determined by the edge determination unit, it can be determined that it is not yet in an idle state. Therefore, the determination by the level determination unit is performed when edge detection is not determined by the edge determination unit. You may make it carry out only to.

Further, when the serial data is configured as a data frame composed of a plurality of unit data, with the data having a predetermined number of bits as unit data, the timing is determined by each unit data as described in claim 5 , for example. At the end of the reception. In this way, the idle state is determined each time reception of unit data is completed, and more efficient determination is possible.

  By the way, the edge detected by the edge detecting means may be, for example, a rising edge or a falling edge as described above. However, in a general serial communication format, unit data is an active level (L level). Start bits, actual data including a plurality of bits, and inactive level (H level) stop bits.

In this case, for example, when all the actual data portions are at the active level (L level), no falling edge occurs except for the falling edge at the start of the stop bit. For this reason, when the idle determining means operates every time when the reception of the unit data is completed as in claim 5 , if the edge detecting means detects the falling edge, the data is being received. Nevertheless, the falling edge is not detected, so that it may be erroneously determined to be in the idle state.

Therefore, when the idle determination unit is configured to operate every time when reception of unit data is completed, the edge detection unit may detect a rising edge as described in claim 6 . In this way, erroneous determination of the idle state can be suppressed.

In addition, when the idle determination unit is configured to operate every time when reception of unit data is completed, as in the communication device according to claim 5 or 6 , the determination time is, for example, as shown in claim 7 , It may be set to be equal to or longer than the data gap time, which is the time from the end of reception to the start of reception of the next unit data, and less than the time obtained by adding the time corresponding to the data length of the unit data to the data gap time.

  That is, the determination time is set between the end of reception of unit data and the end of reception of the next unit data. In this way, every time unit data is received, the presence / absence of reception of the next unit data after the end of the reception is determined, so that the idle state can be determined more accurately.

Next, the communication device according to claim 8 is a communication device which is connected to a communication partner device via a communication line and can transmit / receive serial data to / from each other, and the serial data is a unit of data of a predetermined number of bits. The data is configured as a data frame composed of a plurality of unit data, and includes an edge time storage means for detecting an edge of received data and storing the time at the time of detection.

  Each time the unit data is received, the first time calculation means obtains the latest edge detection time that is the last time the edge was detected before the end of reception based on the stored contents of the edge time storage means. The unit data reception end time is calculated based on the latest edge detection time and the number of received bits from the last detected edge to the end of reception of the unit data.

  Further, the second time calculating means calculates a time obtained by adding at least the data gap time and the time corresponding to the data length of the unit data to the calculated reception end time as the idle determination time. The idle determination means determines that the communication line is in an idle state when no unit data is received between the reception end time and the idle determination time. As described above, the data gap time is the time from the end of reception of unit data to the start of reception of the next unit data.

According to the communication apparatus configured for idling determination means makes the determination based on accurate reception end time and idle determination time calculated by the first and second time calculation means, according to claim 2, wherein A serial communication method is realized, and as in claim 2 , it is possible to perform normal serial communication by detecting the idle state of the communication line, and also to accurately perform idle determination even when the communication speed is increased. It becomes. For example, for a microcomputer that does not have hardware for determining an idle state but has an edge time storage means, it functions as a first time calculation means, a second time calculation means, and an idle determination means. By causing the microcomputer to execute the program, it becomes possible to determine the idle state in software.

More specifically, the communication device having the above configuration (Claim 8 ) can be configured as described in Claim 9 , for example. That is, it includes a time measuring unit that outputs a signal indicating that when the set time comes, and the idle determination unit further includes a time setting unit and a reception determination unit. The time setting unit sets the idle determination time calculated by the second time calculating unit in the time measuring unit every time reception of the unit data ends, and the reception determination unit confirms that the idle determination time has come from the time measuring unit. When the signal shown is output, it is determined whether or not unit data has been received between the time when the idle determination time is set and the time when the signal is output. And when it determines with the reception determination part not having received, it determines with a communication line being an idle state.

In the communication device according to claim 8 or 9 , the edge time storage means may store the time when the rising edge is detected. In this way, as in the case of the communication device of claim 6 , it is possible to more reliably prevent the case where the edge detection time is not stored despite communication being performed, and to suppress erroneous determination of the idle state. It becomes possible.

Preferred embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of an in-vehicle serial communication system according to an embodiment to which the present invention is applied. As shown in FIG. 1, the in-vehicle serial communication system of the present embodiment is mainly for registering data necessary for preventing theft of the vehicle, and includes a tool 10, an engine ECU 20 and an immobilizer mounted on the vehicle. The ECU 30 is connected to the communication line L1 for serial data communication.

  The tool 10 sends a personal identification code or the like stored in the microcomputer 11 to the communication line L1 via the transmission buffer 12, and transmits serial data transmitted on the communication line L1 to the microcomputer 11 via the reception buffer 13. Configured to input.

  The engine ECU 20 is an ECU for controlling an engine of a vehicle (not shown), and serial data transmitted on the communication line L1 is input to the microcomputer 21 via the reception buffer 23, and the serial data output from the microcomputer 21. Is sent to the communication line L1 via the transmission buffer 22.

  The immobilizer ECU 30 is an ECU that performs various control related to security such as theft prevention. The serial data transmitted on the communication line L1 is input to the microcomputer 31 via the reception buffer 33 and output from the microcomputer 31. The serial data is transmitted to the communication line L1 via the transmission buffer 32.

  The format of serial data transmitted on the communication line L1 in the in-vehicle serial communication system of this embodiment is the same as the format shown in FIG. 16, and one frame (data frame) is composed of a plurality of 1-byte data. The For this reason, the serial code sent from the tool 10 and each ECU 20, 30 to the communication line L1 including the above-mentioned code is in the format shown in FIG. Each 1-byte data constituting the frame corresponds to the unit data of the present invention. In the present embodiment, the interval of each 1-byte data constituting the frame (data gap interval of the present invention) is almost zero and is transmitted continuously.

  And the flow of the frame at the time of immobilization registration processing in this embodiment, that is, the flow of the frame on the communication line L1 when the personal identification code is registered in each ECU 20, 30 by transmitting the personal identification code from the tool 10. Is as shown in FIG. That is, first, a frame including a password is sent from the tool 10 onto the communication line L1. This frame requests the microcomputer 31 in the immobilizer ECU 30 to register the password.

  When the immobilizer ECU 30 receives the frame from the tool 10, the immobilizer ECU 30 performs various processes such as password registration according to the contents of the frame. Then, after registration, the data indicating the registration and the registered password are sent as response data (frame) to the tool 10 on the communication line L1.

  The engine ECU 20 does not perform substantial processing on the frame from the tool 10 to the immobilizer ECU 30, and registers the password by receiving response data from the immobilizer ECU 30 to the tool 10. After the registration, response data (frame) is returned to the tool 10.

  By performing predetermined processing such as password code registration as described above, the anti-theft system comes to function. That is, when an electronic key in which a password is stored is inserted into a key cylinder (not shown), the password is verified by the microcomputer 31 in the immobilizer ECU 30 and the microcomputer 21 in the engine ECU 20. The description is omitted.

  Transmission / reception of serial data as described above is controlled by the microcomputers 11, 21, 31 included in the tool 10 and the ECUs 20, 30. Hereinafter, the configuration for serial communication in each of these microcomputers will be described. However, the microcomputers 11, 21, and 31 included in the tool 10 and the ECUs 20 and 30 are only focused on the configuration and operation for controlling serial communication. Basically, both are the same. For this reason, the microcomputer 31 included in the immobilizer ECU 30 will be described as an example.

  As shown in FIG. 2, the microcomputer 31 provided in the immobilizer ECU 30 communicates with a ROM 42 that stores a program, a CPU 41 that executes a program stored in the ROM 42, and a RAM 43 that temporarily stores calculation results by the CPU 41. A communication unit 45 that receives serial data on the line L1 via the reception buffer 33 and the data input port P2 and transmits serial data on the communication line L1 via the data output port P1 and the transmission buffer 32, and reception data RxD An edge detection unit 46 for detecting the edge of the timer, a timer 44 for measuring the time based on a command from the CPU 41 and generating a timer interrupt processing request W2 when the set time has elapsed, and a bus connecting the above-described units 47.

  The communication unit 45 is a general asynchronous serial communication interface, and includes a reception register and a transmission register (not shown). When 1 byte (= 8 bits) of data is written to the transmission register by the CPU 41, serial data in an asynchronous format using the data as effective data (that is, from all 10 bits of the configuration described in FIG. 16). 1 byte data) is sequentially output to the transmission buffer 32 as transmission data TxD and sent to the communication line L1.

Further, the communication unit 45 receives the 10-bit serial data (1-byte data) transmitted on the communication line L1 by the reception register, and when the reception is completed (that is, the 1-bit data is stored in the reception register). When byte data is stored), a reception interrupt processing request W1 is generated.

For this reason, the CPU 41 can transmit the data onto the communication line L1 by writing 1-byte data in the transmission register of the communication unit 45, and when the reception interrupt processing request W1 is generated from the communication unit 45, The received data can be acquired by transferring 1 byte (8 bits) of valid data from the receiving register of the communication unit 45 to the RAM 43 or the like.

  The edge detection unit 46 receives the reception data RxD received via the reception buffer 33 via the edge detection port P3. When an edge occurs in the reception data RxD, the fact is held. In the present embodiment, the rising edge is detected. Specifically, as shown in FIG. 4, every time reception of 1 byte data is completed, the rising edge detection state is reset to L level. Thereafter, when a rising edge occurs, the rising edge detection state is detected and the rising edge detection state becomes H level. Become. Thereafter, the H level state is maintained until reset is performed again.

  Here, for example, when predetermined data (frame) is transmitted from another microcomputer and is received by the microcomputer 31 of the immobilizer ECU 30, reception of each 1-byte data constituting the frame is performed as described above. The CPU 41 actually performs processing based on the received data after receiving all 1-byte data for one frame. Therefore, after the start of frame reception, the microcomputer 31 needs to determine that all the frames have been received, that is, that the communication line L1 has entered an idle state.

  In the case of the conventional microcomputer 100 described in FIG. 17, as described above, the idle detection unit 108 that is hardware for detecting the idle state is provided in the communication unit 104 in advance. Based on the detection result, it was possible to easily know whether or not the engine was in the idle state.

  However, none of the microcomputers 11, 21, and 31 according to the present embodiment is provided with hardware for detecting an idle state. Therefore, in order to perform serial communication using the microcomputer 31, it is necessary to take hardware or software measures so that the user or the like can determine the idle state by some method.

  Therefore, in this embodiment, the microcomputer 31 is initially provided with the edge detection unit 46, the timer 44, and the like to determine the idle state in software. That is, by incorporating a program for determining the idle state into the ROM 42 (for example, an electrically rewritable ROM such as an EEPROM), the CPU 41 determines the idle state.

  Next, among the communication operations of the in-vehicle serial communication system of the present embodiment, the idle state determination operation will be described with reference to FIG. However, in FIG. 4, for the sake of simplification of explanation, a case where one frame composed of two 1-byte data whose data gap time is zero is illustrated.

  As shown in FIG. 4, when reception of the first 1-byte data ends at time t1, the communication unit 45 generates a reception interrupt processing request W1. Receiving this, the CPU 41 resets the rising edge detection state in the edge detection unit 46 and sets the timer 44 to a predetermined determination time T. Thereafter, the second 1-byte data is received. In this example, the first 5 bits including the start bit are at the L level and the 6th bit is at the H level, and a rising edge occurs (time t2). Therefore, the rising edge detection state becomes H level at time t2.

Thereafter, when the determination time T set in the timer 44 elapses and the time t3 is reached, the timer 44 generates a timer interrupt processing request W2 . Receiving this, the CPU 41 sees the rising edge detection state at that time, and is at the H level (that is, when a rising edge occurs during the timer timing period) or at the logic level of the communication line L1 that is at the L level. That is, if the logical level of the received data RxD corresponds to either the active level (L level), it is determined that data is still being received.

  When the reception of the second 1-byte data is completed at time t4, the rising edge detection state is reset and the timer 44 is reset by the reception interrupt processing request W1 again as at time t1. Thereafter, when the determination time T elapses and time t5 is reached, the CPU 41 looks at the rising edge detection state by the timer interrupt processing request W2, but at this time, since the reception of the frame has already ended in this example, the time t4 Thereafter, no rising edge occurs. Moreover, the communication line L1 is in an inactive state (H level). Thus, the CPU 41 determines that the reception of the frame is completed and the communication line L1 is in an idle state, and turns on the reception completion flag.

  Next, a process executed by the microcomputer 31 in order to realize the above-described determination of the idle state will be described based on FIGS. 5 and 6 is executed by the CPU 41 of the microcomputer 31, and a program for each process is stored in the ROM.

  First, FIG. 5 shows a case where the CPU 41 generates a reception interrupt processing request W1 by the communication unit 45 (that is, when 1-byte data is received in the reception register of the communication unit 45). Then, it is a flowchart which shows the reception interruption process which starts execution at the time t1 and the time t4).

  When the reception interrupt process is started, first, in step (hereinafter abbreviated as “S”) 110, the rising edge detection state in the edge detection unit 46 is initialized to L level. In step S120, the timer 44 is set to the determination time T, and in step S130, the received 1-byte data is processed (for example, transfer from the reception buffer to the RAM 43).

  Note that the determination time T set in the timer 44 in S120 may be appropriately determined within a range in which the determination time T elapses from the start of reception of the next 1-byte data to the end of reception of the 1-byte data. Good. That is, for example, when set at time t1 in FIG. 4, the determination time T passes between the reception start time of the next 1-byte data (approximately time t1 in this example) and the reception end time t4. That's fine.

  In the present embodiment, the timer 44 is set aiming at the approximate center of the next one-byte data. Of course, this is an example, and may be set aiming at the end of one-byte data, for example. . However, if it is set just before the end of reception of 1-byte data, there is a risk that the reception interrupt processing will be delayed by the timer interrupt processing. Therefore, it is preferable to set the timer 44 (set the determination time T) aiming at the approximate center of the next 1-byte data as in this example.

  Next, FIG. 6 is a flowchart showing the timer interrupt process. This timer interrupt process is performed when the determination time T set in the timer 44 in S120 of the above reception interrupt process (FIG. 5) has elapsed (time t3 and time t5 in the example of FIG. 4). When the CPU 41 receives the generated timer interrupt processing request W2, the CPU 41 starts execution.

  When this timer interruption process is started, first, in S210, the rising edge detection state in the edge detection unit 46 is checked. At this time, if a rising edge is detected, the interrupt process is terminated as it is. If not detected, the process proceeds to S220. In S220, it is determined whether or not the logical level of the communication line L1 is L level. If it is L level, it is determined that data is being received and this interrupt process is terminated. If it is H level, the process goes to S230. move on.

  When the process proceeds to S230, no rising edge is detected during the determination time T, and since the communication line L1 is inactive when the determination time T has elapsed, reception of data (frame) is completed. The reception completion flag is set by determining that the idle state is established. In subsequent S240, reception completion processing (various processing based on the received frame), transmission preparation processing, and the like are performed.

  As described above, in the in-vehicle serial communication system according to the present embodiment, each of the microcomputers 11, 21, 31 for controlling serial communication executes a reception interrupt process every time reception of 1-byte data is finished, and the timer 44. Is set to the determination time T, and after the determination time T has elapsed, it is determined whether or not the engine is in the idle state by timer interruption processing. The determination is first made by determining whether or not a rising edge has occurred during the determination time T. If not, the determination is further made by looking at the logic level of the communication line L1.

  Therefore, according to the in-vehicle serial communication system of the present embodiment, even if the microcomputer does not have hardware for detecting the idle state, the functions such as the edge detection unit 46 and the timer 44 provided in the microcomputer are used. Thus, the idle state can be determined in software, and serial communication can be normally performed.

  In addition, the presence or absence of a rising edge from the end of reception of 1-byte data until the determination time T elapses is detected, and the timer 44 is set so that the determination time T elapses near the center of the next 1-byte data. Is set, and the logic level of the communication line L1 when the determination time T has elapsed is also used as the determination material in the idle state. Therefore, if data is being received, that fact can be reliably detected. Can reliably determine that it is in the idle state.

Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. In the present embodiment, each of the microcomputers 11, 21, and 31 corresponds to the communication device of the present invention, the edge detection unit 46 corresponds to the edge detection unit and the detection state holding unit of the present invention, and the CPU 41 corresponds to the present invention (claims). Item 3 ) corresponds to the idle determination means, and the timer 44 corresponds to the time measuring means of the present invention (Claim 4 ).

  In the reception interrupt process of FIG. 5, the process of S110 corresponds to the process executed by the detection state initialization unit of the present invention, and the process of S120 corresponds to the process executed by the time measurement starting unit of the present invention. In the timer interrupt process of FIG. 6, the process of S210 corresponds to the process executed by the edge determination unit of the present invention, and the process of S220 corresponds to the process executed by the level determination unit of the present invention.

[Second Embodiment]
In the first embodiment, the example in which the rising edge detection function (edge detection unit 46) provided in the microcomputer 31 is used for the determination of the idle state has been described. However, depending on the type of the microcomputer, whether or not data reception is in progress is described. Some are equipped with a hardware determination function (hereinafter referred to as a “receiving determination function”). In this embodiment, the microcomputer having a receiving determination function as described above, so that a determination is made idle by utilizing the function. This will be described in detail below.

  FIG. 7 shows a schematic configuration of the microcomputer 50 of the present embodiment. Similarly to the microcomputer 31 shown in FIG. 2, the microcomputer 50 of the present embodiment is also provided for controlling serial communication in the tool 10 and the ECUs 20 and 30 constituting the in-vehicle serial communication system of FIG. Except for the unit 53, the hardware configuration is basically the same as that of the microcomputer 31 of FIG. Therefore, the same components as those of the microcomputer in FIG. Although the microcomputer 50 of the present embodiment also includes the edge detection unit 46 as in the microcomputer 31 of FIG. 2, it is not shown in the present embodiment because it is not involved in the determination of the idle state.

  The communication unit 53 included in the microcomputer 50 is different from the communication unit 45 in FIG. 2 in that the receiving determination unit 54 implements the receiving determination function in hardware. The CPU 51 can determine whether or not data (1-byte data) is being received by viewing the determination contents of the receiving determination unit 54. Specifically, as shown in FIG. 8 (details will be described later), a reception flag is set when a start bit of 1-byte data is detected, and reception of 1-byte data is terminated when a stop bit is detected. The receiving flag is cleared.

In the present embodiment, the microcomputer 50 as described above is provided from the beginning, by using the timer 44 and receiver in the determination unit 54 or the like, so that it is determined by software idle. That is, by incorporating a program for determining the idle state in the ROM 52, the CPU 51 determines the idle state.

  Next, among the communication operations of the in-vehicle serial communication system according to the present embodiment, an idle state determination operation will be described with reference to FIG. FIG. 8 also illustrates a case where one frame made up of two 1-byte data with a data gap time of zero is received for the sake of simplicity, as in FIG. 4 of the first embodiment.

  As shown in FIG. 8, when reception of the first 1-byte data starts, a receiving flag is set at time t1. When this 1-byte data is completed, the receiving flag is cleared and the communication unit 53 generates a reception interrupt processing request W1. Receiving this, the CPU 51 sets the timer 44 at a predetermined determination time T.

Thereafter, in order to receive the second 1-byte data, the receiving flag is set again at time t3. When the determination time T set in the timer 44 elapses and the time t4 is reached, the timer 44 generates a timer interrupt processing request W2 . Receiving this, the CPU 51 looks at the state of the receiving flag to determine whether or not it is receiving. Here, since the reception flag is set at time t4, it is determined that reception is still in progress.

  When the reception of the second 1-byte data is completed at time t5, the receiving flag is cleared and the timer 44 is set by the reception interrupt processing request W1 as at time t2. Thereafter, when the determination time T elapses and time t6 is reached, the CPU 51 looks at the reception flag by the timer interrupt processing request W2, but at this time, no data is received and the flag is cleared. Therefore, the CPU 51 determines that the reception of the frame is completed and the communication line L1 is in an idle state, and turns on the reception completion flag.

  Next, processing executed by the microcomputer 50 to realize the above-described determination of the idle state will be described with reference to FIGS. The processing shown in FIGS. 9 and 10 is executed by the CPU 51 of the microcomputer 50, and a program for each processing is stored in the ROM 52.

  First, FIG. 9 shows a case where the CPU 51 generates a reception interrupt processing request W1 by the communication unit 53 (that is, when 1-byte data is received in the reception register of the communication unit 53, and the example of FIG. FIG. 5 is a flowchart showing a reception interrupt process that starts executing at time t2 and time t5).

  When this reception interrupt process is started, first, the timer 44 is set to the determination time T in S310. In subsequent S320, the received 1-byte data is processed (for example, transfer from the reception buffer to the RAM 43). The determination time T set in the timer 44 in S310 is the same as that in the first embodiment.

  Next, FIG. 10 is a flowchart showing the timer interrupt process. This timer interrupt process is performed when the determination time T set in the timer 44 in S310 of the above reception interrupt process (FIG. 9) has elapsed (time t4 and time t6 in the example of FIG. 8). When the CPU 51 receives the generated timer interrupt processing request W2, the CPU 51 starts execution.

  When this timer interrupt process is started, first, in S410, it is determined whether or not a receiving flag is set, that is, whether or not 1-byte data is being received. At this time, if the receiving flag is set, the interrupt processing is terminated as it is, but if it is not set, it is determined that the reception of data (frame) is completed and the idle state is set. In S420, the reception completion flag is set. In subsequent S430, reception completion processing, transmission preparation processing, and the like are performed.

  As described above, in this embodiment, the serial communication control microcomputer 50 configuring the in-vehicle serial communication system executes the reception interrupt process every time the reception of 1-byte data is finished, and determines the timer 44 for the determination time. It is set to T, and after the determination time T elapses, it is determined whether or not it is in an idle state by timer interruption processing. The determination is made by looking at the receiving flag when the determination time T has elapsed.

  Therefore, according to the in-vehicle serial communication system of the present embodiment, even if the microcomputer does not have hardware for detecting the idle state, the receiving determination function (receiving determination unit 54) included in the microcomputer, etc. Can be used to determine the idle state in software, and serial communication can be performed normally.

In addition, since the idle state is determined based only on reception when the determination time has elapsed, it is possible to determine the idle state with a reduced processing load .

[Third Embodiment]
In the first embodiment, the CPU 41 executes the reception interrupt process in response to the reception interrupt process request W1 generated at the end of reception of 1-byte data, thereby resetting the rising edge detection state and setting the timer 44. I made it. However, the reception interrupt process may not be executed immediately when the reception interrupt process request W1 is received, and may be started after a predetermined interrupt waiting time has elapsed. If the start of the reception interrupt process is delayed due to such an interrupt waiting time, the reception interrupt process will not be executed even though the reception of the next 1-byte data has already started. There is a possibility that the rising edge until the processing is started cannot be detected and the idle state is erroneously determined.

  This problem is more likely to occur as the communication speed becomes higher, and in the case of very high speed communication, in some cases, when several bits of the next one-byte data are already received, the previous 1 It is possible that reception interrupt processing for byte data is started.

  Therefore, in the present embodiment, the reception end time of 1-byte data is accurately calculated and received at the reception end time so that the idle state can be determined stably and accurately even when the communication speed becomes high. The idle state is determined by checking the state (waiting for reception processing). This will be described in detail below.

  FIG. 11 shows a schematic configuration of the microcomputer 60 of the present embodiment. Similarly to the microcomputer 31 shown in FIG. 2, the microcomputer 60 of the present embodiment is also provided for controlling serial communication in the tool 10 and the ECUs 20 and 30 constituting the in-vehicle serial communication system of FIG. Except for the configuration of 63 and the input capture module 72, the hardware configuration is basically the same as the microcomputer 31 of FIG. Therefore, the same components as those of the microcomputer in FIG. In the present embodiment, when the rising edge is detected by the edge detection unit 46, the rising edge interrupt processing request W3 is generated.

  In the timer 63 provided in the microcomputer 60 of the present embodiment, the CPU 61 sets a free-run counter (hereinafter referred to as “FRC”) 71 that is always counted up by an internal clock of the microcomputer and time information obtained by calculation of the CPU 61 described later. The output compare register (hereinafter referred to as “OCR”) 74 is compared with the current time that is the count value of the FRC 71 and the time information set in the OCR 74. When the two match, the timer interrupt processing request W2 is issued. And a comparator 75 for generating. In the present embodiment, “time” refers to the count value of the FRC 71.

  Further, the microcomputer 60 of the present embodiment includes an input capture module (hereinafter referred to as “ICM”) 72 that detects the rising edge of the received data RxD and stores the value of the FRC 71 at the time of detection. That is, the reception data RxD input via the reception buffer 33 is input to the ICM 72 via the input capture input port P4 as well as the data input port P2 and the edge detection port P3. When the ICM 72 detects a rising edge, the value of the FRC 71 at the time of detection is stored in an input capture register (hereinafter referred to as “ICR”) 73. The value of this ICR 73 is updated every time a rising edge is detected. For this reason, the latest rising edge detection time is always stored in the ICR 73.

  In the present embodiment, as described above, using the timer 63, the ICM 72, the edge detection unit 46, and the like that are included in the microcomputer 60 from the beginning, the determination of the idle state is performed in software. That is, by incorporating a program for determining the idle state into the ROM 62, the CPU 60 determines the idle state.

  Next, among the communication operations of the in-vehicle serial communication system according to the present embodiment, an idle state determination operation will be described with reference to FIG. Similarly to FIG. 4 of the first embodiment, FIG. 12 exemplifies a case where one frame composed of two 1-byte data having a data gap time of zero is received for the sake of simplicity.

  As shown in FIG. 12, when reception of the first 1-byte data starts, every time a rising edge is detected by the ICM 72, the detection time (the value of the FRC 71) is stored in the ICR 73. Specifically, the value of FRC 71 is taken in and stored in ICR 72 at times t1, t2, and t3. Based on the time stored in the ICR 73 (that is, the time t3) and the bit length from the time t3 to the end of reception (here, the time for one bit) when the reception of the 1-byte data is completed. The reception end time t4 is calculated.

  Although it is possible to obtain the reception end time by fetching the value of the FRC 71 by an interrupt process or the like at the end of reception, the FRC 71 immediately after starting the interrupt process simultaneously with the end of reception as described above. It is very difficult to capture the value of. For this reason, the time obtained by the interrupt process is a time delayed from the time when the reception is actually finished, to some extent. Therefore, in this embodiment, an accurate reception end time is obtained by adding the bit length from the edge detection time to the end of reception to the accurate edge detection time stored in the ICR 73. At this time, the time t3 stored in the ICR 73 is, in other words, the time when the last rising edge is detected before the end of reception.

Then, by adding a time corresponding to the 1- byte data length (that is, a time corresponding to 10 bits) to the calculated accurate reception end time t4, if 1- byte data is received next, the 1- byte data Next reception end time (NextTime1) is obtained, which will just end reception. Then, the next reception end time NextTime 1 obtained is set in the OCR 74.

As for the next 1- byte data, the detection time is stored in the ICR 73 every time a rising edge is detected. On the other hand, in the comparator 75, the next reception end time NextTime1 set in the OCR 74 is compared with the value of the FRC 71 that is periodically counted up, and almost the same timing as the end of reception of the one- byte data ( At time t8), the difference between the two becomes 0 and a timer interrupt processing request W2 is generated. Of course, a reception interrupt processing request W1 is also generated upon completion of reception. When each of the interrupt processing requests W1 and W2 is generated, a flag (reception interrupt waiting flag and timer interrupt waiting flag) indicating that the interrupt processing is waiting is set.

  The CPU 61 first executes an interrupt process for a request received first out of the reception interrupt process request W1 and the timer interrupt process request W2 that are generated almost simultaneously. That is, for example, if the reception interrupt process request W1 is slightly early, the process is executed from the reception interrupt process, and during that time, the timer interrupt process is in a waiting state.

  If timer interrupt processing is performed first, it is determined whether or not reception interrupt is waiting in the interrupt processing, and if it is waiting for reception interrupt, the timer interrupt processing is terminated. Receive interrupt processing. On the other hand, in the reception interrupt process, similar to the process at time t4 described above, the reception end time is calculated, and the next reception end time NextTime2 is calculated based on the calculated reception end time and set in the OCR 74. Clear the timer interrupt wait flag.

  After that, at time t9 (= NextTime2), timer interrupt processing is executed. At this time, since data reception has already been completed and the reception interrupt wait flag has not been set, it is determined to be in an idle state. Set the reception completion flag.

  That is, when the reception interrupt process is executed first, the next reception end time NextTime is calculated and set in the OCR 74, and the timer interrupt process is not performed. On the other hand, when the timer interrupt process is executed first, the process proceeds to the reception interrupt process if the reception interrupt is waiting, but if it is not waiting for the reception interrupt, the idle state is determined.

  Next, processing executed by the microcomputer 60 in order to realize the above-described determination of the idle state will be described with reference to FIGS. The processes shown in FIGS. 13 to 15 are all executed by the CPU 61 of the microcomputer 60, and the program for each process is stored in the ROM 62.

  First, FIG. 13 is a flowchart showing a rising edge interrupt process executed by the CPU 61 in response to a rising edge interrupt process request W3 generated when a rising edge is detected by the edge detection unit 46. When this process is started, the time taken in the ICR 73 is set in the RAM 43 as a variable “INTTIME” in S610. When a rising edge occurs, the ICM 72 also captures the detection time in the ICR 73. In short, every time a rising edge is detected, the value of ICR 73 that is the detected accurate time is stored in the RAM 43 by the rising edge interrupt process.

  Next, FIG. 14 is a flowchart showing a reception interrupt process that is started when the CPU 61 generates a reception interrupt process request W1 by the communication unit 45 (time t4 and time t8 in the example of FIG. 12). . However, when the timer interrupt process (FIG. 15) is being executed, the process waits for an interrupt process, and the execution starts after the timer interrupt process ends.

When this reception interrupt process is started, first, the received 1-byte data is acquired in S510. In S520, the number of “1” s (H level bits) continuously arranged from the most significant bit is set in the variable “N” based on the acquired bit string of 1-byte data. For example, the first 1-byte data in FIG. 12 is “01100010”. Therefore, the number of “1” s continuously arranged from the most significant bit is zero, and in this case, N = 0 is set. In the case of the next 1-byte data, “11101111” is set, so N = 3 is set.

  After setting “N” in this way, the reception end time is calculated in S530. Specifically, the time from the last rising edge to the end of reception is obtained by adding the time for one bit to N + 1, that is, the number of bits from the last rising edge to the end of reception. Further, the reception end time is obtained by adding the obtained time to the value of “INTTIME”, that is, the last rising edge detection time before the end of reception.

Referring to FIG. 12, for example, the calculation of the time t4 at the end of the reception of the first 1- byte data is performed by adding the subsequent number of bits (1 bit) to the rising edge detection time t3 immediately before that. Is called. Also, the calculation of the time t8 at the end of reception of the next 1- byte data is performed by adding the rising edge detection time t7 immediately before that and the time corresponding to the number of bits (4 bits) thereafter.

  In S540, the next reception end time NextTime is calculated by adding the time of 10 bits (that is, the time of 1-byte data) to the reception end time calculated in S530. This next reception end time NextTime corresponds to the idle determination time of the present invention. Thus, for example, in the reception interrupt process at time t4 in FIG. 12, the next reception end time NextTime1 is calculated, and in the reception interrupt process at time t8, the next reception end time NextTime2 is calculated. .

  After calculating the next reception end time NextTime in this way, the process proceeds to S550, and it is determined whether or not the timer interruption waiting flag is being set. If it is not set, the process proceeds to S570 as it is. If it is being set, the flag is cleared in S560, and then the process proceeds to S570. In step S570, the next reception end time NextTime calculated in step S540 is set in the OCR 74. In step S580, the reception interruption waiting flag is cleared, and the reception interruption process ends.

  Next, FIG. 15 is a flowchart showing the timer interrupt process. In this timer interrupt process, a timer interrupt process request W2 generated by the comparator 75 when the value of the FRC 71 coincides with the time set in the OCR 74 in S570 of the above reception interrupt process (FIG. 14) is sent to the CPU 61. Is received by the CPU 61. However, when the reception interrupt process (FIG. 14) is being executed, the process waits for an interrupt process, and the execution is started after the reception interrupt process is completed.

  When this timer interrupt process is started, it is first determined in S710 whether or not a reception interrupt wait flag is set. As described above, the reception interrupt processing request W1 and the timer interrupt processing request W2 are generated almost simultaneously. Therefore, even if the timer interrupt processing is executed first with a slight difference, the processing of S710 is performed. When it is performed, the reception interrupt waiting flag is already set. Therefore, as long as data is being received, an affirmative determination is made in S710 and the process proceeds to S740, where the timer interrupt wait flag is cleared and the timer interrupt process is terminated.

  On the other hand, when the frame reception is completed (for example, at time t9 in FIG. 12), since the reception interrupt waiting flag is cleared, it is determined as an idle state and the process proceeds to S720 to set the reception completion flag. Then, after the reception completion process and the transmission preparation process are executed in S730, the process proceeds to S740.

  As described above, in this embodiment, the serial communication control microcomputer 60 constituting the in-vehicle serial communication system executes the reception interrupt process every time reception of one-byte data is completed, and the reception end time thereof. Is calculated accurately, and the next reception end time NextTime which is the reception end time of the next 1-byte data is calculated and set in the OCR 74. Then, the idle state is determined depending on whether or not the reception interrupt waiting flag is set when the set next reception end time NextTime is reached.

  Therefore, according to the in-vehicle serial communication system of this embodiment, even if the microcomputer does not have hardware for detecting an idle state, the input capture function (ICM72) and output compare function ( The idle state can be determined by software using the timer 63) and the like, and serial communication can be normally performed.

  Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. In this embodiment, the ICM 72 corresponds to the edge time storage means of the present invention, the CPU 61 corresponds to the idle determination means of the present invention, and the timer 63 corresponds to the time measuring means of the present invention. Further, in the reception interrupt process of FIG. 14, the processes of S520 and S530 both correspond to the processes executed by the first time calculating means of the present invention, and the process of S540 is executed by the second time calculating means of the present invention. This process corresponds to the process, and the process of S570 corresponds to the process executed by the time setting unit of the present invention. In the timer interrupt process of FIG. 15, the process of S710 corresponds to the process executed by the reception determination unit of the present invention.

The embodiment of the present invention is not limited to the above-described embodiment, and it goes without saying that various forms can be adopted as long as it belongs to the technical scope of the present invention.
For example, the edge to be detected when performing edge detection in the first embodiment and the third embodiment is a rising edge, but is not limited thereto, and may be a falling edge, for example. However, in order to more reliably determine the idle state, it is preferable to use a rising edge.

  In each of the above embodiments, one byte data is composed of 10 bits, and a plurality of one byte data are continuously transmitted and received. However, the number of bits constituting one byte data is 10 bits. In addition, the 1-byte data may be transmitted and received at a predetermined interval.

  Further, in each of the above embodiments, the case where serial data is transmitted and received between three ECUs has been described as an example, but it goes without saying that the number of ECUs connected to the communication line L1 (specifically, serial communication) The number of microcomputers that control the above and the type thereof are not particularly limited.

It is a block diagram which shows schematic structure of a vehicle-mounted serial communication system. It is a block diagram which shows schematic structure of the microcomputer of 1st Embodiment. It is a time chart for demonstrating the flow of the flame | frame at the time of the immobility registration process in the vehicle-mounted serial communication system of 1st Embodiment. It is a time chart for demonstrating the communication operation | movement of the vehicle-mounted serial communication system of 1st Embodiment. It is a flowchart which shows the reception interruption process of 1st Embodiment. It is a flowchart which shows the timer interruption process of 1st Embodiment. It is a block diagram which shows schematic structure of the microcomputer of 2nd Embodiment. It is a time chart for demonstrating the communication operation | movement of the vehicle-mounted serial communication system of 2nd Embodiment. It is a flowchart which shows the reception interruption process of 2nd Embodiment. It is a flowchart which shows the timer interruption process of 2nd Embodiment. It is a block diagram which shows schematic structure of the microcomputer of 3rd Embodiment. It is a time chart for demonstrating the communication operation | movement of the vehicle-mounted serial communication system of 3rd Embodiment. It is a flowchart which shows the rising edge interruption process of 3rd Embodiment. It is a flowchart which shows the reception interruption process of 3rd Embodiment. It is a flowchart which shows the timer interruption process of 3rd Embodiment. It is explanatory drawing which shows an example of the data format of serial communication. It is a block diagram which shows schematic structure of the conventional microcomputer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Tool, 11, 21, 31, 50, 60, 100 ... Microcomputer, 12, 22, 32 ... Transmission buffer, 13, 23, 33 ... Reception buffer, 20 ... Engine ECU , 30 ... Immobilizer ECU, 41, 51, 61 ... CPU, 42, 52, 62 ... ROM, 43 ... RAM, 44, 63 ... Timer, 45, 53 ... Communication unit , 46... Edge detection unit, 47, 56, 64... Bus, 54... Receiving determination unit, 71... Free-run counter (FRC), 72 .. input capture module (ICM), 73 ... Input capture register (ICR), 74 ... Output compare register (OCR), 75 ... Comparator, 108 ... Idle detector, L1 ... Communication line, P1 ... D Data output port, P2 · · · data input port, P3 · · · Edge detection port, P4 · · · input capture port

Claims (10)

A serial communication method for transmitting and receiving serial data between a plurality of communication devices connected via a communication line,
The communication device determines whether or not an edge of the received data is detected at a predetermined timing after the start of reception of the serial data until a predetermined determination time elapses from the timing. If the edge is not detected before the time elapses, and the logic level of the communication line is not an active level when the determination time has elapsed, the communication line is in an idle state. A serial communication method characterized by determining. A serial communication method for transmitting and receiving serial data between a plurality of communication devices connected via a communication line,
The serial data is configured as a data frame composed of a plurality of the unit data, with data having a predetermined number of bits as unit data, and further, from the end of reception of the unit data to the start of reception of the next unit data. Time as data gap time
The communication device
Each time an edge of received data is detected, the detection time is stored,
Each time the unit data is received, the reception of the unit data is performed based on the detection time of the edge detected immediately before the end of the reception and the number of received bits from the edge to the end of the reception of the unit data. Calculate end time,
A time obtained by adding at least the time corresponding to the data gap time and the data length of the unit data to the reception end time is set as an idle determination time,
A serial communication method comprising: determining that the communication line is in an idle state when the unit data is not received between the reception end time and the idle determination time . A communication device connected to a communication partner device via a communication line and capable of transmitting / receiving serial data to / from each other,
  Edge detection means for detecting an edge of data received via the communication line;
  It is configured to operate every predetermined timing after the reception of the serial data, and when the edge is not detected by the edge detection means until a predetermined determination time elapses from the timing, And an idle determination means for determining that the communication line is in an idle state when the logical level of the communication line is not an active level when the determination time has elapsed,
  A communication apparatus comprising: The communication device according to claim 3,
  A timing means for timing the determination time;
  When an edge is detected by the edge detection means, detection state holding means for holding information indicating that the edge has been detected;
  With
  The idle determination means includes
  For each of the timings, a timing start unit that starts timing of the determination time by the timing means,
  A detection state initialization unit that initializes the detection state holding means at each timing;
  An edge determination unit that determines whether or not an edge is detected during the determination time based on information held in the detection state holding unit at the end of timing by the timing unit;
  A level determination unit that determines a logical level of the communication line at the time of completion of timing by the timing unit;
  A communication apparatus comprising: The communication device according to claim 3 or 4 ,
The serial data is configured as a data frame composed of a plurality of the unit data, with data having a predetermined number of bits as unit data.
The timing is when reception of the unit data ends.
A communication device. The communication device according to claim 5 ,
The communication device according to claim 1, wherein the edge detecting means detects a rising edge . The communication device according to claim 5 or 6,
The determination time is equal to or longer than a data gap time that is a time from the end of reception of the unit data to the start of reception of the next unit data, and corresponds to the data length of the unit data in the data gap time. A communication device characterized in that it is less than or equal to the time added . A communication device connected to a communication partner device via a communication line and capable of transmitting and receiving serial data to and from each other.
The serial data is configured as a data frame composed of a plurality of the unit data, with data having a predetermined number of bits as unit data, and further, from the end of reception of the unit data to the start of reception of the next unit data. Time as data gap time
Edge time storage means for detecting an edge of received data and storing the time at the time of detection;
Every time the unit data is received, the latest edge detection time, which is the time when the edge was last detected before the end of reception based on the stored contents of the edge time storage means, is obtained, and the latest edge detection time, First time calculating means for calculating the reception end time of the unit data based on the number of received bits from the last detected edge to the end of reception of the unit data;
Second time calculation means for calculating, as idle determination time, a time obtained by adding at least the data gap time and a time corresponding to the data length of the unit data to the reception end time calculated by the first time calculation means. When,
Idle determination means for determining that the communication line is in an idle state when the unit data is not received between the reception end time and the idle determination time;
A communication apparatus comprising: The communication device according to claim 8 ,
It has time measuring means to output a signal indicating that when the set time is reached,
The idle determination means includes
A time setting unit that sets the idle determination time calculated by the second time calculating means in the time measuring means each time reception of the unit data is terminated;
When the signal indicating that the idle determination time set by the time setting unit is reached is output from the time measuring unit, the unit data is set between the time when the idle determination time is set and the time when the signal is output. A reception determination unit that determines whether or not
And determining that the communication line is in an idle state when it is determined that the reception determination unit has not received the communication line . The communication device according to claim 8 or 9, wherein
The edge time storage means stores a time when a rising edge is detected .

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