JPH0879225A - Data communication system and data communication method - Google Patents

Abstract

PURPOSE: To provide a data communication system capable of performing bidirectional data transfer by one data signal line. CONSTITUTION: Master communication equipment connected to one data communication line outputs a transfer direction bit 212 for instructing the transfer direction of communication data following the output of a start bit 211 to the data communication line and the master communication equipment or a slave communication equipment receives transfer data from the data communication line or outputs transmission data to the data communication line as needed corresponding to the level (instruction) of the transfer direction bit. Then, a data transmission side equipment outputs a stop bit 214 when the transmission of the data is ended.

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 and method, and more particularly to a data communication system and method for performing serial data communication.

[0002]

2. Description of the Related Art Conventionally, devices for performing serial data communication are connected to each other by a signal line for transferring data from the communication device A to the communication device B and a signal line for transferring data from the communication device B to the communication device A. Thus, bidirectional data transfer is realized by connecting the two communication lines in this manner.

[0003]

However, in the above-mentioned conventional example, since the two or more signal lines are required to connect the communication device, the cost of the wire rod is high.

[0004]

The present invention has been made in order to solve the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, a data communication system in which at least two data communication devices are connected to one data communication line, wherein at least one data communication device connected to the data communication line is connected to the data communication line. Transmission instruction means for outputting a data transfer direction instruction for instructing the transfer direction of the communication data to the data communication line, and receiving the transfer data from the data communication line as necessary according to the instruction by the transmission instruction means, or A first data transmission / reception unit for outputting transmission data to the data communication line, and determining to the other data communication device connected to the output communication line the data transfer direction instruction from the data communication line. Depending on the judgment means and the judgment result of the judgment means, the output data is output to the data communication line as necessary or is transferred from the data communication line. Characterized in that it comprises a second data transmitting and receiving means for receiving data.

For example, the data communication to the data communication line is serial data communication, and the data transfer direction instruction by the transmission instructing means is a level signal indicating the data transfer direction. The transmission instructing means outputs a transfer direction bit indicating the data transfer direction instruction after the start bit.

Further, for example, the first data transmitting / receiving means outputs the transmission data following the output of the transfer direction bit by the transmission instructing means, and outputs a stop bit after the end of the data output. The second data transmission / reception communication means is characterized in that, at the time of data transmission from the own device, the transmission data is output following the reception of the transfer direction bit by the transmission instruction means, and the stop bit is output after the data output is completed. The start bit, the transfer direction bit, and the stop bit are output at substantially the same time.

[0007]

With the above structure, the direction of the data communication can be controlled by instructing the data transfer direction prior to the data communication, so that the bidirectional data transfer can be performed by one data signal line. There is.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment according to the present invention. Here, in order to distinguish the two communication devices, one is called a master communication device 110 and the other is called a slave communication device 120. FIG. 2 shows an example of the communication format used in the data communication between the master communication device 110 and the slave communication device 120 and the signal level of the communication data on the signal line 101 in the present embodiment.

As shown in FIG. 2, the communication format of this embodiment has a start bit 211 and a transfer direction bit 21.
2. Transfer data 213 including data check bits and stop bits 214. That is, in this embodiment, a transfer direction bit 212 indicating the transfer direction is added to the normal communication format, and the transfer direction bit 21 is added.
When 2 is "high level", the slave communication device 120
It indicates that the data is transferred to the master communication device 110. When the transfer direction bit 212 is "low level", the data is transferred from the master communication device 110 to the slave communication device 120. Therefore, in this embodiment, by checking the transfer direction bit 212, it is possible to recognize from which device the data has been sent, and it is possible to carry out the phase direction communication using one data communication line.

Control circuit 111 of master communication device 110
Internal signal line 114 when data needs to be transmitted.
Start bit 21 is sent to the transmission register 112 via
1, the transfer direction bit 212, the transfer data 213 including the data check bit, and the stop bit 214 are stored in the transmission register 112. After that, the control circuit 111 applies a serial clock to the transmission register 112 via the internal signal line 115 to start data transfer.

When a serial clock is applied to the transmission register 112, the transmission register 112 starts to output the transmission data set via the open drain (or open collector) output buffer 113.
First, a start bit is output to the communication signal line 101. Upon receiving the start bit from the communication signal line 101 via the input buffer 127 and the internal signal line 130, the control circuit 121 of the slave communication device 120 starts the receiving operation. Then, the transmission register 112 sets the transfer direction bit 21.
When 2 is placed on the communication signal line 101 via the open drain output buffer 113, the control circuit 121 receives the transfer direction bit 212 via the input buffer 127 and the internal signal line 130, and determines the data transfer direction. To do.

When the data transfer direction is from the master communication device 110 to the slave communication device 120,
The control circuit 121 causes the reception register 126 to store the internal signal line 12
The serial clock is applied via 9 and the transfer data 213 transferred thereafter is received. That is, when the transfer register 112 transmits the transfer direction bit and then transfers the transfer data to the communication signal line 101 via the open drain output buffer 113, the data is stored in the reception register 126 via the input buffer 127. . The serial reception data stored in the reception register 126 can be taken out from the internal signal line 128 as parallel data.

Further, the control circuit 1 of the mask communication device 110
The storage unit 11 stores at least the start bit 211 and the transfer direction bit 212 in the transmission register 112 via the internal signal line 114 when it becomes necessary to receive data.
After that, the control circuit 111 applies a serial clock to the transmission register 112 via the internal signal line 115 to start data transfer.

When the serial clock is applied, the transmission register 112 outputs the start bit 211 initially set in the transmission register 112 to the communication signal line 101 via the open drain (or open collector) output buffer 113. To do. Upon receiving the start bit 211 from the communication signal line 101 via the input buffer 127 and the internal signal line 130, the control circuit 121 of the slave communication device 120 starts the receiving operation.

Subsequently, when the transmission register 112 sends the transfer direction bit 212 to the communication signal line 101 via the open drain output buffer 113, the control circuit 121 passes this transfer direction via the input buffer 127 and the internal signal line 130. The bit 212 is received and the data transfer direction is determined. When it is determined that the data transfer direction is the transfer from the slave communication device 120 to the master communication device 110, the control circuit 121 sends the transmission data 213 and the stop bit 214 to the transmission register 122 via the internal signal line 124. Data is stored and data transmission is started by applying a serial clock to the internal signal line 125.

The data output from the transmission register 122 is output to the communication signal line 101 via the open drain (or open collector) output buffer 123. The data output to the communication signal line 101 is input to the master communication device 110 via the input buffer 117 and stored in the reception register 116 in synchronization with the serial clock applied to the internal signal line 119. The serial reception data stored in the reception register 116 can be taken out from the internal signal line 118 as parallel data.

The resistor 141 is a pull-up resistor. Details of the communication format used for communication of the signal line 101 of the present embodiment will be described with reference to FIG. The start bit 211 and the transfer direction bit 212 are always transmitted by the master communication device 110 (201, 204). If transfer direction bit 212 indicates a transfer from master communication device 110 to slave communication device 120, master communication device 110 sends transfer data 213 (204) and slave communication device 120 does not send data (20).
5). The transfer direction bit 212 is the slave communication device 120.
From the master communication device 110 to the master communication device 110, the slave communication device 120 transmits the transfer data 213 (202), and the master communication device 110 does not transmit the data (201). Since the output of the master communication device and the output of the slave communication device are directly connected to the output of the open drain (or open collector), the output is a negative logic wired OR. Therefore, the signal sent to the communication signal line 101 is 203 , 206.

FIG. 3 is a flow chart showing the communication procedure of the master communication device 110. Master communication device 110
When the need for transmission or reception occurs, first transmits the start bit 211 (S301), and then transmits the transfer direction bit 212 (S302). It is determined whether the data transfer is from the master communication device 110 to the slave communication device 120 (S303). In the case of data transfer from the master communication device 110 to the slave communication device 120, data transmission is started (S314). It is determined whether all the data to be transmitted has been transmitted (S315), and if there is still transmission data, the data transmission is continued (S314),
When all the data has been transmitted, a stop bit is transmitted (S316), and the process ends.

On the other hand, if the transfer is not from the master communication device 110 to the slave communication device 120 in S303, data reception is started (S304). It is determined whether the received data is a stop bit (S305), if it is not a stop bit, data reception is continued (S304), and if it is a stop bit, reception is ended. FIG. 4 is a flowchart showing a communication procedure of the slave communication device 120.
The slave communication device 120 receives the start bit 211 (S401) and then the transfer direction bit 212 (S402). Based on the transfer direction bit 212, it is determined whether the data is transferred from the master communication device 110 to the slave communication device 120 (S403). If the data is not transferred from the master communication device 110 to the slave communication device 120, the control mode 121 of the slave communication device 120 is used because the transmission mode is closer to the slave communication device 120.
Starts data transmission (S414). It is determined whether all the data to be transmitted has been transmitted (S415), and if there is still transmission data, the data transmission is continued (S414),
If all the data has been transmitted, the stop bit 214 is transmitted (S416) and the next start bit 211 is waited for (S401).

If the transfer is from the master communication device 110 to the slave communication device 120 in S403, data reception is started (S404). Then, it is judged whether the received data is the stop bit 214 (S405), and if it is not the stop bit, the data reception is continued (S40).
4) If it is a stop bit, reception is ended and the next start bit is waited for (S401).

In the present embodiment, by providing the above-mentioned configuration and control, bidirectional data transfer is possible with one signal line only by adding simple control.

[0022]

[Other Examples]

[Second Embodiment] In the above-described first embodiment, FIG.
As described above, the open-drain (or open-collector) output buffers 113 and 123 are used as the output driver to the signal line 101, but the present invention is not limited to the above example and a 3-state buffer may be used. . A second embodiment according to the present invention using a 3-state buffer as an output buffer to the signal line 101 will be described below.

FIG. 5 is a diagram showing a second embodiment according to the present invention in which a 3-state buffer is used as an output buffer for the signal line 101. In FIG. 5, the same components as those shown in FIG. 1 of the first embodiment described above are designated by the same reference numerals and detailed description thereof will be omitted. Reference numerals 513 and 523 are 3-state output buffers. By using the 3-state output buffers 513 and 523 as shown in FIG. 5, it is possible to achieve the same effect as that of the first embodiment.

[Third Embodiment] In the above-described first embodiment, an example has been described in which the transmission register 113 and the reception register 116 of the master communication device 110 are operated by separate clock signals, but the present invention is the above example. However, the same effect as that of the above-described embodiment can be achieved even if the transmission register 113 and the reception register 116 of the master communication device 110 are operated by the same clock signal. FIG. 6 shows a third embodiment of the present invention configured as described above. In the example of FIG. 6, the same serial clock signal is supplied to the transmission register 113 and the reception register 116 via the internal signal line 115 to operate both registers.

With the above construction, the same operational effects as those of the first embodiment described above can be achieved, and since the single clock is used, the control becomes easy. The present invention may be applied to a system including a plurality of devices or an apparatus including a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0026]

As described above, according to the present invention, since the data communication direction can be controlled by giving the data transfer direction instruction prior to the data communication, the bidirectional communication is performed by one data signal line. Is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment according to the present invention.

FIG. 2 is a schematic diagram showing how communication is performed in this embodiment.

3 is a flowchart showing a communication procedure of the master communication device shown in FIG. 1 of the present embodiment.

FIG. 4 is a flowchart showing a communication procedure of the slave communication device shown in FIG. 1 of the present embodiment.

FIG. 5 is a block diagram showing a configuration of a second exemplary embodiment according to the present invention.

FIG. 6 is a block diagram showing a configuration of a third exemplary embodiment according to the present invention.

[Explanation of symbols]

101 communication signal line 110 master communication device 111, 121 control circuit 112, 122 transmission register 113, 123 open drain (or open collector) output buffer 114, 115, 118, 124, 125, 128, 1
29,130 Internal signal line 116,126 Reception register 117,127 Input buffer 141 Pull-up resistor 201,204 Master communication device output signal 202,205 Slave communication device output signal 203,206 Serial signal 211 Start bit 212 Transfer direction bit 213 Transfer Data 214 Stop bits 513,523 3 State output buffer

Claims (11)

[Claims] 1. A data communication system in which at least two data communication devices are connected to one data communication line, wherein the data is connected to at least one data communication device connected to the data communication line. Transmission instruction means for outputting a data transfer direction instruction for instructing the transfer direction of the communication data to the communication line to the data communication line, and receiving transfer data from the data communication line as necessary according to the instruction by the transmission instruction means Or a first data transmission / reception unit for outputting transmission data to the data communication line, and for instructing another data communication device connected to the output communication line, the data transfer direction from the data communication line. And output data to the data communication line as necessary according to the result of the judgment of the judgment means or the data communication line. Second for receiving Rino transfer data
A data communication system, comprising: 2. The data communication according to claim 1, wherein the data communication with respect to the data communication line is serial data communication, and the data transfer direction instruction by the transmission instructing means is a level signal indicating a data transfer direction. system. 3. The data communication system according to claim 2, wherein the transmission instruction means outputs a transfer direction bit indicating the data transfer direction instruction after a start bit. 4. The first data transmission / reception means outputs the transmission data following the output of the transfer direction bit by the transmission instruction means, and outputs a stop bit after the end of the data output. 3. The data communication system according to 3. 5. The second data transmission / reception communication unit outputs the transmission data following the reception of the transfer direction bit by the transmission instruction unit at the time of the data transmission from the own device, and outputs the stop bit after the end of the data output. The data communication system according to claim 3, wherein: 6. The data communication system according to claim 4, wherein the start bit, the transfer direction bit, and the stop bit are output at substantially the same time. 7. A data communication method in a data communication system in which at least two data communication devices are connected to one data communication line, the data indicating a transfer direction of communication data to the data communication line. A transfer direction instruction is output from at least one data communication device connected to the data communication line, and the data communication line-connected data communication device follows the data transfer direction instruction to transfer data from the data communication line as necessary. Or a transmission data is output to the data communication line. 8. The data communication method according to claim 7, wherein the data communication with respect to the data communication line is serial data communication, and the data transfer direction instruction is a level signal indicating a data transfer direction. 9. The data communication method according to claim 8, wherein the data transfer direction instruction is a transfer direction bit indicating a data transfer direction instruction following a start bit. 10. The data communication method according to claim 9, wherein the data communication device outputs the transmission data subsequent to the output of the transfer direction bit, and outputs the stop bit after the end of the data output. 11. The data communication method according to claim 10, wherein the star, the bit, the transfer direction bit, and the stop bit are output at substantially the same time.