JPH0720160B2 - Data communication method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of mutually transmitting serial data or parallel data between a pair of communication stations, and in particular, a data communication method adopting contention type transmission control. It is about.

(Prior Art) When performing data communication between a pair of information devices (for example, a computer system), in order to avoid contention due to transmission requests from both devices, the main station to which data is to be transmitted is avoided. It is necessary to decide which slave station receives the data. Also, after the master station and the slave stations are decided,
In order to reliably transmit and receive data, the master station and slave stations need to synchronize with each other.

23 and 24 show a conventional data communication system generally called GP-IB.

The communication system is equipped with a controller that creates a command for determining the master station and the slave station. As shown in FIG. 23, the control signal AT from the controller to the slave station (reception side) is provided.
After a predetermined sequence of control signals NRFD and NDAC from M and DAV, slave station to master station (transmission side), the controller sends command data DI01 to 8 to the slave station (reception side), and the slave station recognizes this. For the first time, data transmission / reception is started.

In transmitting and receiving, as shown in FIG. 24, the control signal ATN sent from the master station to the slave station, the control signal N sent from the slave station to the master station
Data DI01-8 is transmitted from the master station to the slave stations while being synchronized by the three-wire handshake by RFD and NDAC.

(Problems to be solved) However, in the conventional data communication system, the sequence for determining the master station and the slave stations is complicated as shown in FIG. In transmission, as shown in FIG. 24, a so-called 4-edge type handshake is performed in which a pair of falling and rising of each control signal is set as one state change, and the data transmission cycle is the state of the control signal. Since the cycle of the value change (the period from the falling edge to the rising edge) is twice, it takes a long time to transmit the data and there is a problem that the high speed communication corresponding to the high speed processing of the computer cannot be performed.

An object of the present invention is that after one of the stations declares the master station,
It is to provide a data communication system in which the sequence from the other station accepting the slave station until the master station recognizes this is extremely simple and the execution time of the sequence is extremely short.

Another object of the present invention is to adopt a so-called two-edge type handshake in which a falling edge and a rising edge of a control signal are set as one state change at the time of data transmission. It is an object of the present invention to provide a data communication method capable of performing high-speed data transmission by making the data transmission cycle the same as (the period from the fall to the rise) and the data transmission cycle.

(Means for Solving the Problem) In the data communication system according to the present invention, one of a pair of communication devices connected to each other by at least four signal lines is a main station on the transmitting side and the other is a main station on the transmitting side. Is a slave station on the receiving side and performs bidirectional data communication. 4 above
Of the two signal lines, two signal lines are used for transmitting the first control signal CLKOUT and the second control signal STSOUT from the master station to the slave station, and the remaining two signal lines are from the slave station to the master station. The third
It is used for receiving the control signal CLKIN and the fourth control signal STSIN.

After a synchronization phase for determining the master station and the slave stations, data transmission from the master station to the slave stations is started. The synchronization phase includes a first step of changing the states of both the first and second control signals from an initial state in which the first to fourth control signals are set to the same state value, and a first step of realizing the first step. A second step of changing the state of one or both of the third and fourth control signals, and a third step of returning one of the first and second control signals to the original state on the assumption that the second step is realized. And a fourth step of returning the third and fourth control signals to their original states on the assumption that the third step is realized, and transits to the transmission phase only when the fourth step is realized.

Further, when bidirectional communication of parallel data is performed between a pair of communication devices that are mutually connected by four control signal lines and a data bus, in the transmission phase, the first step after completion of the fourth step of the synchronization phase. Through starting the data transmission with the state of the fourth control signal as the initial state, while changing the state of the first control signal CLKOUT at a constant cycle, the state of the third control signal CLKIN is changed on the assumption that the state of the first control signal changes. Then, the data transmission is continued in synchronization with the change of the state of the third control signal.

Furthermore, when bidirectional communication of serial data is performed between a pair of communication devices mutually connected by four signal lines, the signal line of the second control signal STSOUT is used for transmission of serial data in the transmission phase. Then, the fourth of the synchronization phase
The data transmission is started by setting the states of the first to fourth control signals at the completion of the step to the initial state, and the first control signal CL
While changing the state of KOUT at a constant cycle, the state of the third control signal CLKIN is changed on the premise of the state change of the first control signal, and data transmission is continued in synchronization with the state change of the third control signal.

(Operation) When one communication station (master station) does not send data in the synchronization phase, the first step is executed, which causes the master station to send the master station declaration command to the slave station. If the slave accepts this command, the second step is executed, whereby the master detects the slave's consent status. Next, the third step is executed, and the transmission start request command is sent from the master station to the slave station. If the slave accepts this command, the fourth step is executed,
By this, the master station detects the reception ready state of the slave station.

When contention occurs, or when synchronization failure occurs during the execution of the first to fourth steps, each control signal returns to the initial state and the synchronization phase is executed again to eliminate contention. .

When making a transition from the synchronization phase to the transmission phase, the state of each control signal at the completion of the synchronization phase is used as it is as the initial state in the transmission phase, and at the same time as the transition to the transmission phase, transmission of serial data or parallel data is started.

In the transmission phase, a two-edge handshake between the first control signal CLKOUT and the third control signal CLKIN is performed,
Data transmission is performed in the same cycle as the state value change of the first control signal.

Also, in the transmission phase, both the second control signal STSOUT and the fourth control signal STSIN are maintained at the same state value, so that the control signal pattern formed in the four steps of the synchronization phase appears in the transmission phase. And therefore reliable data transmission is guaranteed.

(Effect of the Invention) According to the data communication method of the present invention, the synchronization phase is composed of four extremely simple steps, so that the execution time is short and a quick transition to the transmission phase is possible.

Further, in the transmission phase, data transmission is performed at the same cycle as the state change of the first control signal, so that the transmission speed is increased as compared to the conventional data transmission using the 4-edge handshake.

(Embodiment) Hereinafter, a first embodiment for transmitting parallel data and a second embodiment for transmitting serial data will be described in detail with reference to the drawings.

It should be noted that the examples are for explaining the present invention and should not be understood as limiting the invention described in the claims or reducing the scope.

First Embodiment FIG. 1 shows an example in which a pair of computer systems (1) and (2) are connected by the data communication system according to the present invention, and each computer system has a CPU (3) and a memory. It is composed of a computer body composed of (4) and a communication control circuit (5) for executing a predetermined communication protocol.

The communication control circuits (5) and (5) of both computer systems (1) and (2) have four control lines and an 8-bit data bus DT.
Connected to each other via PORT. The terminals to which the four control lines are connected are the control signal CLKOUT and
It is composed of two output terminals for outputting STSOUT and two input terminals for inputting control signals CLKIN and STSIN indicating acceptance of the slave station.

The communication control circuit (5) is formed of a one-chip LSI, and the second
As shown in the figure, it comprises four blocks of a data bus buffer (6), a read / write logic (7), a control logic (8) and a data port (9). The data bus buffer (6) controls the interface with the CPU (3), and exchanges data between the CPU and the internal bus according to the data direction control signal and the ENABLE signal from the read / write logic (7). It holds data, which enables communication control circuit (5)
It enables the asynchronous operation of the CPU (3). Lead /
The write logic (7) is C under the control of the CPU (3).
It controls the data bus buffer (6) and the data port (9) for the purpose of sending the data D0 to D7 from the PU to the data bus DTPORT through the data port (9) or vice versa. The data port (9) exchanges data between the internal bus and an external device and holds data, and performs signal level conversion and the like as necessary.

The control logic (8) manages and controls three phases, idle, synchronization and transmission, which will be described later, and as shown in FIG. 3, a phase control unit (10), a counter unit (11) and a bus control unit. It consists of three blocks (12). The bus control unit (12) converts the signal level, 4
The control signal lines of the book are controlled and sampled. The phase control unit (10) executes a series of procedures (see FIGS. 12 to 16) for communication control in each phase and transition control between phases, and if necessary, the bus control unit (12). ) Control and activation of the counter unit (11). The counter unit (11) monitors the time for detecting the timeout in each phase.

As shown in FIGS. 4 (a) and 4 (b), the communication protocol formed during transmission control is composed of three basic phases: an idle phase, a synchronization phase, and a transmission phase. The idle phase is a state in which the reception request from the partner station is monitored when there is no transmission request from the own station. The synchronization phase is a state in which the master station (transmission side) and the slave station (reception side) are determined, and the timing adjustment between the master station and the slave station for reliable communication of data is performed in the subsequent transmission phase. Both stations start in the idle phase when the master station notifies the slave station of the reception request.
The transmission phase is a state for transmitting and receiving the number of data frames agreed between the two stations, and starts after the timing adjustment is completed (hereinafter, synchronization establishment) in the synchronization phase.

FIG. 5 shows phase transitions when data transmission (transmission) from the master station to the slave station and data transmission (reception) from the slave station to the master station. When a reception request is issued in the idle phase, the process transits to the reception synchronization phase, and when a transmission request is issued, the process transits to the transmission synchronization phase. When synchronization failure occurs in the reception or transmission synchronization phase, the process returns to the idle phase. When the synchronization is established in the reception synchronization phase or the transmission synchronization phase, the process transits to the reception transmission phase or the transmission transmission phase. When the transmission is completed in the reception or transmission transmission phase or a timeout occurs, the process returns to the idle phase. The procedure for realizing these phase transitions will be described later.

Hereinafter, changes in each control signal in the idle phase, the synchronization phase, and the transmission phase will be described.

Idle phase As indicated by the mark 1 in Fig. 6 (a), if the station has no intention of transmitting, it sets both control signals CLKOUT and STSOUT to 1, and in that state synchronizes with the external reference clock. At this timing, the states of the control signals CLKIN and STSIN from the partner station are checked, and if both are not 0, it is determined that there is no reception request from the partner station, and the idle phase is continued. In the figure
When both CLKIN and STSIN become 0 as indicated by the mark 2., there is a possibility of a reception request from the partner station, so the reception synchronization phase is entered. The parenthesized control signal in FIG. 6 (a) represents the type of control signal for the partner station, and the same applies to the following description and other drawings.

Also, when there is a transmission request from the own station, both CLKOUT and STSOUT are set to 0 on the assumption that both CLKIN and STSIN are 1 as indicated by the mark 2 in Fig. 6 (b). To do. However, if both CLKIN and STSIN are not 1,
STSOUT maintains a high impedance state (not shown) to avoid signal collisions on the data port.

Synchronization phase As indicated by mark 1 in Fig. 7, the slave station (reception side) waits for both the control signals (CLKIN) and (STSIN) to become 0 in the receiving state, and then sends the control signal ( Set CLKOUT) to 1 and (STSOUT) to 0. As shown by mark 2 in the figure,
When CLKIN is 1 and STSIN shifts to 0, the main station (transmission side) considers that the reception side has recognized the transmission start sequence and sets CLKOUT to 1 and STSOUT to 0. If CLKIN is not 1 and STSIN is not 0 within a certain period of time, transition to the idle phase. Further, as indicated by the mark 3 in the figure, the receiving side waits until (CLKIN) becomes 1 and (STSIN) becomes 0, and in the meaning of the transmission phase transition preparation completion notification (CL
Set both (KOUT) and (STSOUT) to 1. If the above state is not reached within a certain period of time, or if another state is detected, the idle phase is entered.

If both stations do not start transmission at the same time and contention occurs, and if a timeout occurs and the process shifts to the idle phase, both stations do not use the reference clocks of the same phase and the same period, so the synchronization phase is executed again. Contention is resolved by this.

In the above synchronization phase, four control signals CLKOUT, STSOUT,
It can be set as pattern matching by changing the state of CLKIN and STSIN, and when a predetermined pattern matching is obtained, synchronization will be established.

Further, a special meaning is given to the pattern of the four signal lines. That is, as shown in FIGS. 10 (a) and 10 (b), CLKOUT and STSOUT are changed from 1 to 0 at the transition (first step) from the time point I (idle phase) to the time point II (synchronous phase). By this, a master station declaration command is formed, and it is indicated that one station has made a master station declaration. Next, in the transition from the time point II to the time point III (second step), while keeping (CLKOUT) at 1,
By changing (STSOUT) from 1 to 0, a slave consent status is formed and represents the slave's consent. Further
In the transition from the time point III to the time point IV (third step), while maintaining STSOUT at 0, CLKOUT is changed from 0 to 1 to form a transmission start request command, and the main station starts transmission. The request is shown. Furthermore, transition from time point IV to time point V (4th step)
In (STSOUT) while keeping (CLKOUT) at 1,
By changing from 0 to 1, the slave station ready status is formed and the slave station is ready to receive (synchronization is established).
Represents.

Since the command and the status are each formed of two control signals, even if a difference occurs in the time required to reach the threshold level due to the electrical characteristics of the control line, accidents due to misidentification are effectively prevented. .

In addition, since synchronization establishment is achieved not only by the master station declaration command and slave station acceptance status but also by the formation of the transmission start request command and the reception preparation completion status, even if contention occurs, data transmission due to misidentification is sure. Will be prevented.

In principle, there may be 36 types of synchronization patterns of the four control signals in the synchronization phase, including those shown in FIGS. 10 (a) and (b), but considering the initial condition value and end condition value. Furthermore, it is necessary to select a pattern that is unlikely to appear in the later-described transmission phase. As the pattern satisfying this condition, the patterns shown in FIGS. 11A and 11B can be adopted in addition to the patterns shown in FIGS. 10A and 10B.

Transmission Phase Data transmission is performed in synchronization with the handshake of the control signal CLKOUT sent by the master station (transmission side) and the control signal CLKIN sent by the slave station (reception side) as shown in FIG.

After successfully passing the synchronization phase, control signals CLKIN and STS
When IN becomes 1 and the transmission start condition is satisfied, 1.
As shown in, the transmitting side sets CLKOUT to 0 and DT
Output the corresponding bit to PORT. The receiving side waits for (CLKIN) to become 0, as shown in 2. in the figure, extracts the corresponding bit from (DTPORT), and sets (CLKOUT) to 0. The transmission side waits for CLKIN to become 0 as shown in 3.
Set OUT to 1 and output the corresponding bit to DTPORT. The receiving side waits for (CLKIN) to become 1 as shown in 4, then extracts the corresponding bit from (DTPORT), and (CL
Set KOUT) to 1. Data is transmitted one after another by repeating the above sequence. In this process, the transmission side aborts the transmission when STSIN changes to 0 as shown in 5. On the receiving side, as shown in 6. (ST
When SIN) becomes 1, it is considered that the other party's transmission is completed.

FIG. 9 shows a series of sequences from the idle phase to the synchronization phase, to the transmission phase from the master station to the slave station, and then to the transmission phase from the slave station to the master station via the synchronization phase. As shown in the figure, the synchronization is established in only two cycles of the state change of the control signal, and the transition to the transmission phase thereafter is performed smoothly, and the data transmission in the transmission phase is the same period as the state change cycle of the control signal. And extremely high-speed data transmission has been realized.

The third step will be described below with reference to the flowcharts of FIGS. 13 to 17.
The procedure registered in the phase control unit (10) in the figure will be described.

As shown in FIG. 12, in the idle phase, it is judged whether or not the signal from the CPU is a transmission request (15), and if YES, it transits to the transmission synchronization phase. If NO, CLKOUT and STSOUT are both 0. It is judged (16). If NO, the process returns to the judgment (15). If YES, the process shifts to the reception synchronization phase.

In the transmission synchronization phase, after starting the state monitoring timer as shown in FIG. 13, it is judged whether both CLKIN and STSIN are 1 while monitoring the time-up of the timer (17), and YES If, CLKOUT and STSOU
Both T are set to 0. After that, while monitoring the time up by the state monitoring timer, CLKIN is 1 and STSIN
Is determined (18), and if YES, CLKOUT
To 1 and STSOUT to 0. Furthermore, while monitoring the time-up by the state monitoring timer, it is judged whether or not both CLKIN and STSIN are 1 (19), and if YES, it shifts to the transmission transmission phase.

On the other hand, in the reception synchronization phase, it is determined whether or not both (CLKIN) and (STSIN) are 0 while monitoring the time-up by the state monitoring timer as shown in FIG. 14 (20).
If YES, (CLKOUT) is set to 1 and (STSOUT) is set to 0. Next, while monitoring the time-up by the state monitoring timer, it is judged whether (CLKIN) is 1 and (STSIN) is 0 (21). If YES, both (CLKOUT) and (STSOUT) are set to 1. After that, it transits to the reception transmission phase.

As shown in Fig. 15, in the transmission and transmission phase 1, CLKIN and STSIN are monitored while monitoring the time up by the state monitoring timer.
Are both 1 (22). If YES, CLKOUT and STSOUT are set to 0 after data transmission. After that, in the transmission transmission phase 2, under time-up monitoring,
It is judged whether CLKIN is 0 and STSIN is 1 (23). If YES, after sending data, set CLKOUT to 1 and STSOUT to 0, and then return to the above judgment (22) under time-up monitoring. .

On the other hand, in the reception / transmission phase 1, as shown in FIG. 16, it is determined whether or not both (CLKIN) and (STSIN) are 0 under the time-up monitoring (24). If YES, after data acquisition,
Set (CLKOUT) to 0 and (STSOUT) to 1. afterwards,
In the reception transmission phase 2, under the time-up monitoring, (CL
Judge whether (KIN) is 1 and (STSIN) is 0 (25), and YES
In the case of (1), after fetching the data, after setting both (CLKOUT) and (STSOUT) to 1, the process returns to the judgment (24) under the time-up monitoring.

By the above procedure, the phase transition and the operation in each phase shown in FIG. 5 are realized.

Second Embodiment In this embodiment, as shown in FIG. 17, a pair of communication control circuits (5
0) Four control signal lines CLKOUT, CLKIN, which connect (50)
After establishing synchronization by STSOUT and STSIN, one signal line STS
Uses OUT (STSIN) as a data line and sets 16 bits to 1
The serial data is transmitted as a frame. In this embodiment, the logical relationship between the signal state values "1" and "0" is set opposite to that in the first embodiment.

The hardware configuration is almost the same as that of the first embodiment, but the data port (9) shown in FIG. 2 is not necessary because of serial transmission.

FIG. 6 (a) in the first embodiment, except that the idle phase and the synchronization phase have opposite logical relationships.
The same sequence as the sequence shown in (b) and FIG. 7 is executed.

For example, in the synchronization phase, as shown in FIG.
After setting KOUT and STSOUT to 0, as shown in 1.
Confirm that CKLIN and STSIN are both 0, and check CLKOUT
Set both STSOUT and STSOUT to 1. Next, the receiving side (CLKI
Wait for both N) and (STSIN) to become 1 and then 2. in the figure.
Set (CLKOUT) and (STSOUT) to 1 as confirmation response as shown in. After that, both CLKIN and STSIN are 1 on the transmitting side.
When it shifts to, it is considered that the receiving side has recognized the transmission start sequence, and CLKOUT and STSOUT are set to 1. If there is no change after a certain period of time, it is considered to be a disconnection. Also, CLKI
If both N and STSIN do not become 1 and other states occur, it is determined that there is a protocol error and the process shifts to the idle phase. Furthermore, on the receiving side, (CLKIN) is 0, (STS
After (IN) becomes 1, both (CLKOUT) and (STSOUT) are set to 0 in the sense of a transmission phase transition preparation completion notification.

In the data transmission phase, a sequence different from that in the first embodiment is executed. Bit transmission is performed in synchronization with the handshake of CLKOUT sent by the transmitter and CLKIN sent by the receiver, as shown in Fig. 19. It

When both CLKIN and STSIN become 0 and the transmission start condition is satisfied, the transmitting side waits until CLKIN becomes 0, sets CLKOUT to 1, and outputs the corresponding bit to STSOUT.
The receiving side waits until (CLKIN) becomes 1, extracts the corresponding bit from (STSIN), and sets (CLKOUT) to 1.
Next, the transmission side waits for CLKIN to become 1, and then sets CLKOUT to 0.
And set the corresponding bit to STSOUT. Furthermore, the receiving side waits until (CLKIN) becomes 0, and then (STSI
Extract the relevant bit from (N) and set (CLKOUT) to 0. The signal (STSOUT) on the receiving side is set to 1 at the start of receiving one frame and set to 0 at the end of receiving.

FIG. 20 shows an example of a signal in which the idle phase, the synchronization phase, the transmission phase, the transmission phase, and the synchronization phase are transitioned in accordance with the above sequence. The first
Similar to the embodiment, the synchronization is established in only two cycles of the control signal, and the subsequent transition to the transmission phase is performed in a steady manner, and the data transmission in the transmission phase is the same as the state change cycle of the control signal. , And extremely high-speed (for example, 60 Kbps) data transmission has been realized.

In the present embodiment, the procedure registered in the phase control unit (10) is
This is the same as that shown in FIG. 14 and FIG. The procedure in the transmission phase will be described below with reference to FIGS. 21 and 22.

As shown in Fig. 21, in the transmission and transmission phase 1, while monitoring the time up by the state monitoring timer, CLKIN, S
It is judged whether both TSIN are 1 (26). If YES, CLKOUT is set to 0 after sending data to STSOUT. After that, in the transmission and transmission phase 2, it is judged whether CLKIN is 0 and STSIN is 1 while monitoring the time-up (27), and YES
In the case of, the data is sent to STSOUT, CLKOUT is set to 10, and then the process returns to the judgment (26) under the time-up monitoring.

On the other hand, in the reception transmission phase 1, as shown in FIG. 22, it is judged whether (CLKIN) is 0 or not under the time-up monitoring (2
8) If yes, after fetching data from (STSOUT), set (CLKOUT) to 0. After that, in the reception transmission phase 2, it is judged whether (CLKIN) is 1 or not under the time-up monitoring (29), and if YES, the data is fetched from (STSOUT) and (CLKOUT) is set to 1 , Return to the judgment (28) under the time-up monitoring.

By executing the above procedure, the phase transition shown in FIG.
Data communication in each phase described above is realized. Incidentally, as in the first embodiment, the signal pattern in the synchronization phase does not occur in the transmission phase, so that no malfunction occurs during data transmission.

In the above data communication method, since the sequence from the master station declaration to the slave station acceptance, the master station transmission start request to the slave station ready to receive is extremely simple, the execution time of the sequence is conventionally In addition to being greatly shortened, the circuit configuration becomes simple when the execution of the sequence is realized by the logic circuit.

Further, by adopting the two-edge handshake at the time of data transmission, the cycle of the control signal and the cycle of data transmission are the same, so that high-speed data transmission is possible.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or limiting the scope. The configuration of each part of the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

For example, although the procedures shown in FIGS. 12 to 16, 21 and 22 are realized by software, they can be realized by hardware.

[Brief description of drawings]

1 to 16 show an example in which the present invention is applied to parallel transmission, FIG. 1 is a block diagram showing the overall device configuration, FIG. 2 is a block diagram showing the configuration of a communication control circuit, and FIG. Is a block diagram showing the circuit configuration of the control logic, FIG. 4 is a time chart showing transition of phases, FIG. 5 is a transition diagram between each phase, and FIGS. 6 (a) and 6 (b) are signals of the idle phase. A time chart showing changes, FIG. 7 is a time chart showing changes in signals in the synchronization phase, FIG. 8 is a time chart showing changes in signals in the transmission phase, and FIG. 9 is changes in signals from the idle phase to the transmission phase. FIG. 10 (a) is a time chart showing a change in the state value of a signal in the synchronization phase, FIG. 10 (b) is a chart showing the same change, FIG. a) is a time chart showing another example of change in state value corresponding to FIG. 10 (a), FIG. 11 (b) is a chart showing the same change example, and FIGS. 12 to 16 show the operation in each phase. Flow chart,
17 to 22 show an example in which the present invention is applied to serial transmission, and FIG. 17 is a block diagram illustrating the configuration of signal lines,
FIG. 18 is a time chart showing changes in signals in the synchronization phase, FIG. 19 is a time chart showing changes in signals in the transmission phase, and FIG. 20 is a time chart showing changes in signals from the idle phase to the transmission phase.
21 and 22 are flowcharts showing the operation in the transmission phase, and FIGS. 23 and 24 are time charts showing changes in signals in the conventional system. (1) (2) ...... Computer system (5) (50) ...... Communication control circuit CLKOUT, CLKIN, STSOUT, STSIN ...... Control signal

Claims (3)

[Claims] 1. A pair of communication devices mutually connected by at least four signal lines, one of which is a transmitting side master station, and the other of which is a receiving side slave station. Of the four signal lines, 2
This signal line is used for transmitting the first control signal CLKOUT and the second control signal STSOUT from the master station to the slave station, and the remaining two signal lines are the third control signal CLKIN from the slave station to the master station. And for receiving the fourth control signal STSIN, and after passing through a synchronization phase for determining the master station and the slave stations, data transmission from the master station to the slave stations is started.
From the initial state in which the control signal is set to the same state value, a first step in which both the first and second control signals are changed in state, and one of the third and fourth control signals is premised on realizing the first step. The second step of changing the state of one or both of them, and the first and second steps assuming the realization of the second step.
A third step of returning one of the control signals to the original state, and a fourth step of returning the third and fourth control signals to the original state on the assumption that the third step is realized,
A data communication method characterized in that a transition to a transmission phase is made only when the fourth step is realized. 2. Among a pair of communication devices mutually connected by four control signal lines and a data bus, any one device is a transmitting side master station and the other device is a receiving side slave station. , A parallel data bidirectional communication method, wherein two signal lines of the four control signal lines are the first from the master station to the slave station.
It is used for transmitting the control signal CLKOUT and the second control signal STSOUT, and the remaining two signal lines are used for receiving the third control signal CLKIN and the fourth control signal STSIN from the slave station to the master station. After passing through the synchronization phase for determining the station and the slave station, a transition is made to a transmission phase for transmitting data from the master station to the slave station, and in the synchronization phase, the first to fourth control signals are initially set to the same state value. A first step of changing the states of both the first and second control signals from the state; and a second step of changing the state of either or both of the third and fourth control signals on the assumption that the first step is realized. A third step of returning either one of the first and second control signals to the original state on the premise of the realization of the second step, and a third step on the basis of the third and fourth control signals on the premise of the realization of the third step. It consists of the fourth step of returning to the state. Transition to the transmission phase only when the fourth step is realized, and in the transmission phase, data transmission is performed with the states of the first to fourth control signals at the completion of the fourth step of the synchronization phase as initial states. At the same time as starting, while changing the state of the first control signal CLKOUT at a constant cycle, change the state of the third control signal CLKIN on the premise of the state change of the first control signal, and synchronize with the state change of the third control signal. A data communication method characterized by continuing data transmission. 3. A pair of communication devices connected to each other by four signal lines, one of which is a transmitting master station and the other of which is a receiving slave station. In the bidirectional communication method, after passing through a synchronization phase for determining a master station and a slave station, a transition is made to a transmission phase in which data is transmitted from the master station to the slave station.
Of the two signal lines, two signal lines are used for transmitting the first control signal CLKOUT and the second control signal STSOUT from the master station to the slave station, and the remaining two signal lines are from the slave station to the master station. The third
The control signal CLKIN and the fourth control signal STSIN are used for reception, the transmission phase uses the signal line of the second control signal STSOUT for transmission of serial data, and the synchronization phase uses
From the initial state in which the first to fourth control signals are set to the same state value, the first step of changing the states of both the first and second control signals, and the third and fourth steps assuming the realization of the first step A second step of changing the state of one or both of the control signals; a third step of returning one of the first and second control signals to the original state on the premise of realizing the second step; Third on the assumption that the steps are realized
And a fourth step of returning the fourth control signal to the original state, and transits to the transmission phase only when the fourth step is realized, and in the transmission phase, when the fourth step of the synchronization phase is completed. Data transmission is started by setting the states of the first to fourth control signals of
While changing the state of the first control signal CLKOUT at a constant cycle, the third control signal CLKI is premised on the state change of the first control signal.
A data communication system characterized in that N is changed in state, and data transmission is continued in synchronization with a change in state of the third control signal.