JPH08191319A - Data communication system - Google Patents

Abstract

PURPOSE: To suppress the occurrence of an error on a communication line and stably communicate data irrelevantly to the length of a cable mutually connecting equipments without requiring any complicated operation by providing detecting means and control means for specific communication error occurrence. CONSTITUTION: The equipment 101 which functions as a slave device and the equipment 102 which functions as a master device are connected by a clock line S101, a TXD line S102, and an RXD line S103 which constitute a serial data communication line. Then the system has the detecting means which detects a communication error occurring on the data communication line during a communication of data between the equipments 102 and 101; and a 1st communication system (synchronous system) or a 2nd communication system (asynchronous system) different from the 1st communication system is set as a communication system between the equipments 102 and 101 according to the detection result and the data are communicated according to the set communication system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication system for transmitting data between a plurality of devices, and in particular, a plurality of devices each having a microprocessor or a serial data communication interface. The present invention relates to a data communication system for selectively performing synchronous or asynchronous serial data communication using a serial data communication line.

[0002]

2. Description of the Related Art Conventionally, as a system for transmitting data between a plurality of devices, a plurality of devices each having a microprocessor or a serial data communication interface are connected via a set of serial data communication lines. There is a system configured to perform various functions in each device by transmitting and receiving data between each device by performing serial data communication with each other.

In the conventional data communication system as described above, for example, a personal computer or the like is connected with other peripheral equipment such as a data communication modem or an input scanner,
In this case, each peripheral device is equipped with an asynchronous serial data communication interface such as RS232C or RS422, which is used to connect to a device such as a personal computer and the personal computer. Data and commands are serially transmitted and received to and from peripheral devices.

Further, the equipment such as a personal computer and the peripheral equipment connected to the personal computer are installed at a short distance, and the equipment can be directly connected to each other without using a connection cable, or a short connection cable or the like can be used. Equipment that can be connected and used is equipped with a synchronous serial interface that operates in synchronization with a high-frequency clock in order to send and receive data and commands at high speed. A device that transmits and receives data and commands between devices has also been put into practical use.

In serial data communication as described above, an interface can be constructed at a lower cost than parallel data communication in both cases of asynchronous type and synchronous type, and for connecting each device. Since the number of connection cables is small, it is advantageous over parallel data communication in that the cost for installing a data communication line can be kept low.

In the above-mentioned asynchronous serial data communication, the distance between the devices is normally several tens of meters at a data transfer rate of 9600 bps, although it depends on the specifications of the driving device used and the wire material of the connection cable. Even if the communication is error-free, synchronous serial data communication, for example, the frequency of the synchronous clock is 1MHz.
Thus, even if the distance between each device is several meters, communication is possible without error.

[0007]

However, as described above, conventionally, either the synchronous type or the asynchronous type is used as the interface used for serial data communication. If there is a distance between the devices to be connected and a long connection cable must be used to connect each device, serial data communication must be performed asynchronously in order to reduce the error rate of data on the communication line. However, in this case, it becomes difficult to increase the data transfer rate, and in order to increase the data transfer rate, serial data communication is performed by a synchronous method. Even in this case, long connection cables can be used to connect each device to reduce the error rate of data on the communication line. No reason, there is a drawback that it is necessary to shorten the distance between devices to be connected.

The present invention has been made in order to solve the above-mentioned conventional problems, does not require a complicated operation, and is independent of the length of a connection cable for connecting devices,
An object of the present invention is to provide a data communication system capable of performing stable data communication while suppressing an error occurrence rate on a communication line.

[0009]

In order to achieve the above object, the data communication system of the present invention transmits and receives data, and at the same time, a master device for controlling the operation of the entire system, and a master device for controlling the operation of the entire system, respectively. In a system including a slave device for transmitting or receiving, and a data communication line for performing data communication between the master device and the slave device, data is transmitted between the master device and the slave device. Detecting means for detecting the occurrence of a communication error on the data communication line during the period when the communication is performed, and the data performed between the master device and the slave device according to the detection result of the detecting means. The communication method is set by setting one of the first communication method and the second communication method different from the first communication method. And it is configured so as to have a control means for controlling so as communicate the data according to the communication method.

[0010]

With the above-mentioned configuration, no complicated operation is required,
Regardless of the length of the connection cable that connects the devices, it is possible to suppress the error occurrence rate on the communication line and perform stable data communication.

[0011]

【Example】

(First Embodiment) First, a first embodiment of the present invention will be described.

FIG. 1 is a block diagram showing the configuration of a data communication system as a first embodiment of the present invention.

In FIG. 1, 101 is a device A, 102 is a device B, and devices A101 and B102 are shown.
Is a clock line S101, a TXD line S102, and an RXD line S1 that form a serial data communication line.
Connected by 03. In the present embodiment, the device A101 is a slave device such as a modem, and the device B102 is a master device such as a controller for controlling the device A101 to perform serial data communication. ,Also,
In FIG. 1, only the configuration related to serial data communication between the device A 101 and the device B 102 is described, other configurations are not shown, and detailed description thereof is omitted.

In FIG. 1, reference numerals 106 and 107 denote drive circuits for serial data communication.
The voltage levels and the like of the signals input and output at 6 and 107 are RS232C and R, which are the standards for serial data communication.
Slightly different depending on specifications such as S422 and RS423.

Reference numerals 103 and 110 denote microprocessors for controlling the communication operation of the device A 101 and the device B 102, respectively, and are configured to input the clocks S104 and S109 respectively input to the drive circuits 106 and 107. .

Reference numerals 104 and 109 denote change-over switches, which are driven by the control signals S115 and S114 output from the microprocessors 103 and 110, respectively.
It is configured to switch the received signal input at 6, 107 to either the asynchronous serial data input terminal or the synchronous serial data input terminal of the microprocessor 103, 110 and output the signal.
S112 represents a signal input to the asynchronous serial data input terminals of the microprocessors 103 and 110.
106 and S113 are microprocessors 103 and 110.
The signal input to the synchronous serial data input terminal of is shown.

Similarly, 105 and 108 are change-over switches, which are synchronized with the asynchronous serial data output terminals of the microprocessors 103 and 110 by control signals S115 and S114 output from the microprocessors 103 and 110, respectively. The serial data output terminal is configured to switch and output a transmission signal to be sent to the drive circuits 106 and 107.
07 and S110 are the microprocessor 103 and S110
The signals output from the asynchronous serial data output terminal of the microprocessor 10 are indicated by S108 and S111.
The signals output from the synchronous serial data output terminals 3, 110 are shown.

Although the microprocessors 103 and 110 in this embodiment respectively have a synchronous serial data communication function and an asynchronous serial data communication function,
In the case where the system of this embodiment is configured by a device equipped with a microprocessor having no communication function, 825
By adding an external serial data I / O element such as 1, a system having the same function as the configuration shown in this embodiment can be realized.

The switching operation sequence between the synchronous serial data communication and the asynchronous serial data communication in the first embodiment will be described below with reference to the operation flowcharts shown in FIGS.

FIG. 2 is an operation flowchart showing the serial data communication process of the device B 102 functioning as a master device in this embodiment, and FIG. 3 shows the serial data communication process of the device A 101 functioning as a slave device in this embodiment. It is an operation | movement flowchart.

First, the serial data communication process of the device B102 functioning as a master device in this embodiment will be described.

As shown in FIG. 2, when the serial data communication process is started by turning on the power of the device B102 functioning as a master device, the device B1 is started.
Reference numeral 02 performs an initializing operation (initial setting operation) in each unit related to the serial data communication function (2 in FIG. 2).
01).

Next, the device A that functions as a slave device
In order to start serial data communication with 101, the microprocessor 110 controls the changeover switches 108 and 109 by the control signal S114 to connect the input terminal and output terminal for synchronous serial data communication to the drive circuit 107 (see FIG. 2). 202), the command data to be transmitted is set in a transmission buffer (not shown), and the synchronous serial data communication function is enabled (203 in FIG. 2).

The transmission command data set in the communication buffer as described above is output from the synchronous serial data output terminal as the signal S111 together with the clock S109, and the output clock S109 and command data S111 are output to the drive circuit 107. Is converted to a level and transmitted to the drive circuit 106 of the device A101,
The level is converted in the drive circuit 106 and input to the clock input terminal and the synchronous serial data input terminal of the microprocessor 103, respectively.

Then, in the microprocessor 103,
Data is output from the synchronous serial data output terminal in synchronization with the input clock S109, and the output data is transmitted to the device B through the drive circuit 106 and the drive circuit 107.
It is input to the synchronous serial data input terminal of the microprocessor 110 of 102.

FIG. 4 is a timing chart showing waveforms of various communication signals in the above-mentioned synchronous serial data communication. As shown in FIG. 4, the clock S109 is synchronous serial data communication. In this case, the level is configured to be kept at a high level during the period when data communication is not performed. With this configuration, serial data communication is performed according to the synchronous serial data communication function. The device A10
You will be informed about 1.

As described above, the device A 101 and the device B 102
When the data transmission / reception according to the synchronous serial data communication function with the device A is completed (204 in FIG. 2), the device A
The command data transmitted from the device 101 is the device B 102.
(1) is temporarily stored in a reception buffer (not shown), the command data once stored in the reception buffer is read out, and first, it is checked whether or not a communication error has occurred (205 in FIG. 2).

That is, in the present embodiment, as a check method, a checksum byte added to the data to be transmitted at the transmitting side is added to the data to be transmitted, a CRC code or the like, and the checksum is added to the data received at the receiving side. It is configured to judge whether or not the serial data communication is normally performed without the occurrence of a communication error by checking whether or not an error has occurred in the data transmitted by using the byte or CRC code. There is a device A1
01 to send status data, and the device B 102 receives the status data, whereby the device A 10
It can also be configured to detect whether or not a communication error has occurred on the one side.

If it is determined at 206 in FIG. 2 that no communication error has occurred, the received command data is processed according to the information or the instruction indicated by the received command data. When data is to be transmitted in accordance with the above, the command data to be transmitted is set in the transmission buffer, the synchronous serial data communication function is enabled, and the processing operation returns to 204 in FIG. 2 (207 and 208 in FIG. 2). .

When it is determined in 206 of FIG. 2 that a communication error has occurred, the microprocessor 110 receives the control signal S114 and changes the switch 10.
8 and 109 are connected, input terminals and output terminals for asynchronous serial data communication are connected to the drive circuit 107, command data to be retransmitted is set in the transmission buffer, and a communication line for communicating the clock S109 is normally set. I / O
By setting it to be used as a port and outputting a low level signal to the communication line, it is notified to the device A101 that the serial data communication system has been switched from synchronous to asynchronous, and asynchronous serial The data communication function is enabled and the processing returns to the processing operation 204 in FIG. 2 (209 and 210 in FIG. 2).

After the above processing is performed, the command data to be transmitted is set in the transmission buffer in 208 of FIG. 2 and then the asynchronous serial data communication function is enabled. .

FIG. 5 is a timing chart showing waveforms of various communication signals in the above-mentioned asynchronous serial data communication. As shown in FIG. 5, the clock S109 is used when asynchronous serial data communication is executed. , The level is configured to be kept at a low level during the period when no data communication is performed. With this configuration, serial data communication is performed according to the asynchronous serial data communication function. Device A
101 will be informed.

Next, the serial data communication process of the device A101 functioning as a slave device in this embodiment will be described.

As shown in FIG. 3, when the serial data communication process is started by turning on the power of the device B102 functioning as a slave device, the device A1 is started.
Reference numeral 01 performs an initialization operation (initial setting operation) in each unit related to the serial data communication function (3 in FIG. 3).
01).

Next, the device A that functions as a master device
In order to start serial data communication with 102, the microprocessor 103 controls the changeover switches 104 and 105 by the control signal S115, and connects the input terminal and output terminal for synchronous serial data communication to the drive circuit 106 (see FIG. 3). 302), the data to be transmitted to the device B102 is set in a communication buffer (not shown), and synchronous serial data communication is enabled (303 in FIG. 3).

Then, the data set in the transmission buffer is read in synchronization with the clock S109 sent from the device B102, and is output as a signal S108 to the device A101 via the changeover switch 105 and the drive circuit 106. .

The sequence of data transmission / reception between the device A 101 and the device B 102 is as described above with reference to FIG.
The description is omitted because it is the same as that described using.

When the data transmission / reception according to the synchronous serial data communication function between the device A101 and the device B102 is completed (304 in FIG. 3), the device B102 is described.
The command data transmitted from the device A101 is temporarily stored in a reception buffer (not shown) of the device A101, the command data once stored in the reception buffer is read out, and first, it is checked whether a communication error has occurred. (305 in FIG. 3).

Since the method of checking the communication error is the same as that described with reference to FIG. 2 as described above, the description thereof will be omitted.

If it is determined at 306 in FIG. 3 that no communication error has occurred, the information or instruction indicated by the received command data is received in the same manner as 207 and 208 in FIG. The processing operation described above is performed, and the next communication sequence is started (307 and 308 in FIG. 3).

If it is determined at 306 in FIG. 3 that a communication error has occurred, status data indicating that a communication error has occurred is transmitted to the device B 102, and the clock input terminal (see FIG. The clock S104 supplied to CLK) is monitored for a predetermined period (3 in FIG. 3).
09, 310).

If the level indicated by the clock S104 does not drop to the low level, the process proceeds to 308 in FIG.
Data to be transmitted next and status data indicating that a communication error has occurred in the same manner as described above are set in the transmission buffer, the synchronous serial data communication function is enabled, and the processing operation returns to 304 in FIG. , Equipment B1
02 that the communication error that has occurred is not recovered, and if the level indicated by the clock S104 falls to the low level, it is determined that the communication error has also occurred on the device B 102 side, and the microprocessor 103 determines that the communication error has occurred. The changeover switches 104 and 105 are controlled by the control signal S115,
The input terminal and the output terminal for asynchronous serial data communication are connected to the drive circuit 106 (311 in FIG. 3), the data to be retransmitted is set in the transmission buffer, and the asynchronous serial data communication function is enabled. By returning to the processing operation of 304, the serial data communication between the device A 101 and the device B 102 will be performed asynchronously thereafter (312 in FIG. 3).

(Second Embodiment) Next, a second embodiment of the present invention will be described.

FIG. 6 is a block diagram showing the structure of a data communication system as a second embodiment of the present invention. In FIG. 6, the structure having the same function as the structure shown in FIG. Use the same number as.

In FIG. 6, reference numerals 601 and 602 respectively denote the device A101 and the device B102 used in this embodiment.
For controlling the communication operation of the microprocessor, the microprocessor having an I / O port for synchronous serial data communication and an I / O port for asynchronous serial data communication assigned to the same terminal. It has a function of selectively switching the terminal to be used for synchronous serial data communication or asynchronous serial data communication by setting a register inside the microprocessor.

Further, in FIG. 6, S601 and S602
Are signal lines respectively connected to the RXD terminal and the TXD terminal of the microprocessor 601. S603 and S6
Similarly, 04 is a signal line connected to the TXD terminal and the RXD terminal of the microprocessor 602, and the clock line S104 is a clock input terminal (CL in the figure) of the microprocessor 601 via the drive circuit 106.
K) and an external input interrupt terminal (INT in the figure) are also connected.

The operation sequence for switching between synchronous serial data communication and asynchronous serial data communication in the second embodiment will be described below with reference to the operation flowchart shown in FIG.

In the second embodiment, with regard to the processing operation of the microprocessor 602 in the device B102 functioning as the master device, the processing operations 202 and 209 of FIG. 2 has been described with reference to FIG. 2 except that the processing operation for selectively using each terminal of the microprocessor for synchronous serial data communication or asynchronous serial data communication is replaced by setting the register of FIG. Since the processing operation is the same, the description is omitted here.

Device A that functions as a slave device
The microprocessor 601 in 101 operates according to the operation flowchart shown in FIG.

That is, as shown in FIG. 7, when the serial data communication process is started by turning on the power of the device B 102 functioning as a slave device,
The microprocessor 601 of the device A101 performs an initialization operation (initial setting operation) in each unit related to the serial data communication function (701 in FIG. 7).

Next, the device A that functions as a master device
In order to start serial data communication with the microprocessor 102, the microprocessor 601 sets registers in the microprocessor so that each terminal is first set to an I / O port for synchronous serial data communication, and data to be transmitted to the device B102. Is set in a communication buffer (not shown), synchronous serial data communication is enabled, and the device B102
The data set in the transmission buffer is read in synchronization with the clock S104 transmitted from the signal line S60.
1, output to the device A 101 via the drive circuit 106 (702 in FIG. 7).

By the way, in this embodiment, a communication error occurs in the synchronous serial data transmission being executed,
When the serial data communication executed by the device B101 functioning as the master device is switched from the synchronous type to the asynchronous type, the clock S10 transmitted from the device B102 is changed.
The level indicated by 9 falls from the high level to the low level, and the signal supplied to the external input interrupt terminal INT via the clock line S104 falls, whereby the microprocessor 601 shifts to the interrupt operation by the external input. Is set.

Reference numerals 704 to 707 in FIG. 7 are operation flowcharts showing an external input interrupt operation routine of the microprocessor 601. The microprocessor 601 receives the external input interrupt terminal IN via the clock line S104.
When the signal supplied to T falls from the high level to the low level to shift to the interrupt operation of the external input (704 in FIG. 7), first, it is set inside the microprocessor to manage the serial data communication method. After the asynchronous communication flag is turned on (705 in FIG. 7), the data to be retransmitted is set in the transmission buffer, and the asynchronous serial data communication function is enabled (706 in FIG. 7), the interrupt operation of the external input is performed. The routine returns to the original operation routine (707 in FIG. 7).

In this embodiment, in order to prevent the microprocessor 601 from shifting to the external input interrupt operation during execution of the serial data communication, the transition to the external input interrupt operation is performed when the serial data communication is performed. Is prohibited (703 in FIG. 7), and when the serial data communication is completed (708 in FIG. 7), the processing operation for permitting the transition to the interrupt operation of the external input is performed (709 in FIG. 7). During the period in which the processor 601 is performing serial data communication, the transition to the external input interrupt operation is prevented.

The sequence of data transmission / reception between the device A 101 and the device B 102 is as described above with reference to FIG.
The description is omitted because it is the same as that described using.

When the transmission / reception of data according to the synchronous serial data communication function between the device A101 and the device B102 is completed and the transition to the interrupt operation of the external input is permitted, the data is transmitted from the device B102. Command data once stored in a reception buffer (not shown) of the device A101, the command data once stored in the reception buffer is read out, and first, it is checked whether a communication error has occurred (Fig. 7 of 710).

Since the method of checking the communication error is the same as that described with reference to FIG. 2 as described above, the description thereof will be omitted.

If it is determined at 711 in FIG. 7 that no communication error has occurred, the asynchronous communication flag set inside the microprocessor is turned on by the above-described external input interrupt operation routine. If it is in the ON state, the serial data communication is switched from the synchronous type to the asynchronous type, and therefore the processing operation returns to 708 in FIG.
01 and the device B102 are asynchronously performed, and when not in the ON state, the processing operation according to the information or the instruction indicated by the received command data is performed (712 and 713 in FIG. 7). ).

If it is determined in 711 of FIG. 7 that a communication error has occurred, status data indicating that a communication error has occurred is transmitted to the device B 102 (715 of FIG. 7). .

Then, in 714 of FIG. 7, data to be transmitted next and status data indicating that a communication error has occurred are set in the transmission buffer in the same manner as described above, and the processing operation of 708 of FIG. 7 is performed. Return, device B102
To the external input interrupt terminal INT of the microprocessor 601 via the clock line S104, and if the level indicated by the signal drops to the low level, the device is notified. It is considered that the communication error has occurred on the B102 side as well, and the microprocessor 601 shifts to the above-mentioned external input interrupt operation routine and sets each terminal to the I / O port for asynchronous serial data communication. Then, the data to be transmitted again is set in the transmission buffer, the asynchronous serial data communication function is enabled, and the process returns to the processing operation of 708 of FIG. Communication will be performed asynchronously.

As described above, in the present embodiment, serial data communication between devices is normally performed synchronously, and when a communication error occurs, the clock line is negated to become a communication partner. By configuring the device to notify the device to switch the serial data communication method to asynchronous, the device to be communicated with can monitor the signal supplied via the clock line and automatically communicate with each other. The communication method can be switched from synchronous to asynchronous, and serial data communication can be performed, and it is judged whether or not a communication error has occurred in the serial data communication being executed by each device itself, and the communication error is detected. If it is determined that the error has not occurred, it is considered that no communication error has occurred because the connection cable between the devices is short and high-speed When serial data communication is performed by a synchronous method that can perform real data communication and it is determined that a communication error has occurred, it is considered that a communication error has occurred because the connection cable between the devices is long and the error rate is low Since the serial data communication is performed asynchronously so that the serial data communication can be performed, the operator of the device does not have to perform complicated operations, and the device itself is optimal regardless of the length of the connection cable between the devices. Serial data communication can be performed by the communication method.

Further, in this embodiment, the signal supplied through the clock line is used as the switching signal for the synchronous and asynchronous serial data communication systems, so that the number of signal lines is not increased. There is also an effect that the serial data communication system can be switched.

[0063]

As described above, according to the present invention, no complicated operation is required, and the occurrence rate of errors on the communication line is suppressed regardless of the length of the connecting cable connecting the devices. Thus, it becomes possible to provide a data communication system capable of performing stable data communication.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a data communication system as a first embodiment of the present invention.

FIG. 2 is an operation flowchart showing a serial data communication process of a device as a master device according to the first embodiment of the present invention.

FIG. 3 is an operation flowchart showing a serial data communication process of a device as a slave device according to the first embodiment of the present invention.

FIG. 4 is a timing chart showing waveforms of various communication signals in the synchronous serial data communication of the present invention.

FIG. 5 is a timing chart showing waveforms of various communication signals in asynchronous serial data communication according to the present invention.

FIG. 6 is a block diagram showing a configuration of a data communication system as a second exemplary embodiment of the present invention.

FIG. 7 is an operation flowchart showing a serial data communication process of a device as a slave device according to the second embodiment of the present invention.

[Explanation of symbols]

101, 102 Equipment 103, 110 Microprocessor 104, 105, 108, 109 Changeover switch 106, 107 Driving circuit S101, S104 Clock line S102 TXD line S103 RXD line S105, S112 Asynchronous serial data input line S106, S113 Synchronous serial data Input line S107, S110 Asynchronous serial data output line S108, S111 Synchronous serial data output line

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area H04Q 9/14 K

Claims (11)

[Claims] 1. A master device for transmitting or receiving data and controlling the operation of the entire system, a slave device for transmitting or receiving data, and a master device and a slave device. In a system including a data communication line for performing data communication between the master device and the slave device, a communication error occurs on the data communication line during the data communication period between the master device and the slave device. The first communication method and the first communication method differ from each other in the data communication method performed between the master device and the slave device according to the detection result of the detection unit and the detection result of the detection unit. And a control means for setting any one of the second communication methods and controlling to perform data communication according to the set communication method. Data communication system, characterized in that. 2. The data communication line includes a signal line for transmitting a synchronous clock, and performs data communication according to the first communication method and data communication according to the second communication method. 2. The data communication system according to claim 1, wherein the states of signals transmitted via the signal line are made different. 3. The data communication system according to claim 1, wherein the data communication is serial data communication. 4. The master device or the slave device,
The data communication system according to claim 1, further comprising a microprocessor that executes data communication. 5. The master device or the slave device,
The data communication system according to claim 1, further comprising a data communication interface that executes data communication. 6. The data communication system according to claim 1, wherein the master device includes a personal computer. 7. The data communication system according to claim 1, wherein the slave device includes a peripheral device that operates by being connected to a personal computer. 8. The data communication system according to claim 1, wherein the first communication system is a synchronous data communication system, and the second communication system is an asynchronous data communication system. 9. The control unit may not have a communication error on the data communication line during a period of data communication between the master unit and the slave unit in the detecting unit. If detected, the first communication method is set as the data communication method performed between the master device and the slave device, and if it is detected that a communication error has occurred, then 9. The method according to claim 8, wherein the second communication method is set as a data communication method between the master device and the slave device, and the data communication is controlled according to the set communication method. Data communication system. 10. The data communication line includes a signal line for transmitting a synchronous clock, and performs data communication according to the first communication method and data communication according to the second communication method. 2. The data communication system according to claim 1, wherein the level of the signal transmitted via the signal line is made different. 11. The detection means uses a data error detection data included in the data communicated between the master device and the slave device, and a communication error has occurred on the data communication line. The data communication system according to claim 1, wherein the data communication system detects the fact.