JPS62190947A - Cyclic transmission system - Google Patents

Abstract

PURPOSE:To transmit data to a specific slave station at a high speed with a constant delay time by interrupting communicating operation which is performed at a current point by delimiter transmission from a main station at every constant time, and accessing a priority station and making a communication during the period. CONSTITUTION:Respective slave stations S2-S6 receive data from the main station and sends data to the main station subsequently. The main station M accesses the respective slave stations S2-S6 cyclically in fixed order on the end of each communication to make a communication. On the other hand, the communicating operation which is performed at a current point of time by delimiter transmission from the main station M is interrupted at constant intervals of time and the main station S accesses the priority station S1 during the periods to make a communication. Consequently, data is transmitted cyclically to the slave stations S2-S6 with a uniform delay time and also sent to the priority station S1 at a higher speed with the constant delay time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to improvements in cyclic transmission systems.

(Summary of the Invention) In this invention, the master station cyclically accesses and communicates with each slave station (excluding priority stations) in a fixed order after waiting for the end of each communication, and the master station sends a delimiter at fixed intervals. By interrupting the communication operation being carried out at that point in time, and accessing and communicating with the priority station during that time, data transmission can be performed with the same delay time for the general slave station, but the priority station can transmit data more easily. Data transmission is performed at high speed and accurately with a constant delay time.

(Prior art and its problems) Conventionally, in this type of cyclic transmission system,
The master station cyclically accesses each slave station in a fixed order after the end of each communication to perform communication, that is, data transmission and reception.

Therefore, as the number of subordinate stations increases,
The result was that the transmission delay time increased equally for all slave stations.

Incidentally, there are cases in which a user wants to perform data transmission at high speed to a certain slave station, but does not need to take transmission delays into account as much for other slave stations.

In such cases, the conventional cyclic transmission system has a problem in that it is not possible to allocate transmission time efficiently.

On the other hand, in this type of cyclic transmission system, the method of speeding up data transmission only for a specific slave station is as follows.
For example, it is possible to increase the number of transmissions by the relevant slave station during one transmission cycle, but in this case, since the time required for transmission to each station usually varies, only the transmission delay time to the specified slave station is held constant. The problem is that I can't.

(Object of the Invention) The object of the present invention is to transmit data to a large number of slave stations with equal delay time, while transmitting data to a specific slave station at higher speed and with a constant delay time. The purpose of this invention is to provide a cyclic transmission system that enables the following.

(Structure and Effect of the Invention) In order to achieve the above-mentioned purpose, the present invention allows the master station to send each slave station (excluding priority stations) one after another in a fixed order after each communication is completed.
The system is characterized in that while accessing and communicating with the network, the communication operation being carried out at that time is interrupted by sending a delimiter from the main station at regular intervals, and during that time, the priority station is accessed and communicated. be.

According to such a configuration, data can be transmitted to a large number of slave stations with equal delay times, while data can be transmitted to a specific slave station at a higher speed and with a fixed delay time. can.

(Description of Embodiments) FIG. 1 is a block diagram showing the configuration of the system of the present invention.

As shown in the figure, in this embodiment system, six slave stations S1 to S6 are provided for the master station M, and these are connected to the transmission line L.
11 reception lines L2, and data transmission is performed using a multi-drop transmission method or the like.

In addition, in this example, slave station 1 is defined as a priority station, and only priority station S1 is faster than other slave stations 82 to S6.
Moreover, data transmission is performed with a certain delay time.

FIG. 2 is a block diagram showing the hardware configuration of the master station M and one slave station 3n.

As shown in the figure, the main station M has a CPU 10. System program memory 11. Keyboard display controller 1 to roller 12, work memory 13. It is composed of a programmable timer LSI 14, a communication LSI 15, etc., and functions as, for example, a remote I10 base unit of a programmable controller.

The slave station Sn is C, which is also composed of a microprocessor.
PU20. System program memory 21.1 node memory 22. It consists of an input/output device 23, a communication LSI 24, etc., and functions as, for example, a remote I10 unit of a programmable controller.

The master station M and the slave station Sn are connected to the transmission line L4. Communication is carried out via a reception line L2.

Next, FIGS. 3 and 4 are flowcharts showing the configuration of the control program of the master station M (7) 1i, and FIG. 5 is a flowchart showing the configuration of the control program of the slave station 3n. Please refer to these flowcharts below. The operation of the system of the present invention will be systematically explained.

First, the operation of the main station M will be explained. After going through an initialization process (not shown) and entering steady state operation, the main station M first creates transmission data to the corresponding polling address (step 300), and when the creation is completed, sets a transmitting flag (step 301), and then sends the data. Data is transmitted character by character (step 302).

Here, the polling addresses are updated by +1 from #2 to #6.

Furthermore, as shown in FIG. 7, one block of transmission data includes an address section each consisting of one character;
In addition to the command section and length section, it consists of a data area consisting of multiple keys.

Then, when all galactors have been sent (step 3
03M), clears the sending flag, and then sets the receiving flag (step 304).

On the other hand, on the slave station S2 side corresponding to the polling address,
In the flowchart of FIG. 5, after address matching is performed (steps 500 to 502>), data sent from the main station M is continuously received on the condition that it is not a delimiter (steps 503 and 504). ,5
05,506>.

Here, as shown in FIG. 7, one character of the transmission data includes a start bit bO, command/data fields b1 to b7. Delimiter bit bB, parity bit b9. A stop bit b10 is set to "1" to indicate delimiter transmission.

Therefore, in step 505, it is determined whether the received character is a delimiter by referring to the contents of the delimiter pit b8.

Once all characters have been received in this way (
Step 506), and predetermined processing is performed depending on the content of the received data (Step 507). This processing is, for example, an operation such as outputting output data sent from the remote I10 base unit, which is the master station, to the outside from the input/output device 23 of the remote I10 unit, which is the slave station.

When this operation is completed, transmission data creation processing is subsequently performed (step 508). In this process, for example, input data is read from the input/output device 23 of the remote I10 unit that is the slave station, and the input data is transferred to the remote I10 unit that is the master station.
This process involves editing the data to be sent to the base unit.

When the transmission data creation process is completed, the created data is sent in the same manner as in the case of the main station, while confirming that no delimiter is received during that time (step 510, negative).
One character at a time (step 509) is transmitted to the main station.

When the transmission of all characters is completed (step 511), the process returns to step 503 described above to enter the reception standby state again.

On the other hand, as shown in FIG. 3, the master station enters a reception standby state following completion of transmission (step 305), and receives data from the slave station in response to the slave station's transmission processing (step 509). Upon completion of reception, the receiving flag is cleared (step 306), and the process moves to post-reception processing (step 307).

In this process, for example, various necessary processes are executed on the I10 memory of the programmable controller based on input data sent from a remote I10 unit that is a slave station.

In this way, once the processing of steps 300 to 307 is completed for polling address #2,
Thereafter, the polling address is communicated with #3, #4, . . . #6 one by one, and the processes from step 300 to step 307 are repeated each time.

Furthermore, each of the slave stations 83 to S6 receives data from the master station by sequentially performing the processing shown in the flowchart of FIG. 5, and then transmits data from the slave station to the master station. It is.

By repeating the above process, from the master station M to each slave station S.
2 to S6 are cyclically accessed and communicated in a fixed order, waiting for the end of each communication.

On the other hand, in the present invention, during the above-described cyclic communication, the communication operation being carried out at the time is interrupted by delimiter transmission from the main station M at regular intervals, and during that time, the main station M accesses the priority station S1. and communicate with each other.

The interrupt transmission cycle information necessary for this periodic communication processing is stored in the programmable timer LS, 114 according to the input signal from the keyboard display controller 12, and the programmable timer LS114 outputs an interrupt signal for each interrupt transmission cycle. It is sent to the CPU 10.

Then, as shown in the flowchart of FIG. 4, scheduled transmission and reception processing is performed by the transmission timer interrupt.

In this process, it is first determined whether or not the main station M is transmitting and receiving. If neither transmitting nor receiving is being performed (step 400, negative), transmission data to the priority station S1 is immediately created (step 404). ), and transmits this one character at a time (step 405), waits for the transmission to end (step 406), and enters a reception standby state (step 4).
07).

Then, as shown in the flowchart of FIG. 5, on the priority station S1 side, after receiving data from the main station (steps 503 to 506), on the condition that the addresses are matched (steps 500 to 502), The above-mentioned post-reception process is performed (step 507), then transmission data is created (step 508) and sent back to the main station (steps 509-511).

Then, as shown in the flowchart of FIG. 4, the main station M side receives data from the priority station S1 (step 407), and upon completion of reception, executes post-reception processing (step 408). The process returns to the normal processing shown in the figure.

Note that in this case (that is, if no transmission/reception is being performed at the time of starting υj), the delimiter transmission process (step 409) is internally skipped, and no delimiter transmission is performed.

On the other hand, a particularly important point in this invention is that when the scheduled transmission/reception processing is started by the transmission timer interrupt, if transmission/reception is in progress with any of the slave stations S2 to S6 (step 40 ON fixed), the delimiter transmission is performed (step 401). This delimiter transmission is performed by setting delimiter pit b8 to "1", as shown in FIG.

At this time, if the master station M is transmitting, this delimiter transmission is immediately received by the slave station that is receiving at that time (the fifth
After that, the slave station waits for the next delimiter transmission from the master station (step 512).

On the other hand, if the main station M is receiving data when the scheduled transmission/reception process is started by a transmission timer interrupt, after transmitting the delimiter (step 401), it enters a waiting state for two characters (step 402). , 403)
, and then moves on to the process of creating transmission data to the priority station (
Step 404).

As shown in FIG. 5, each time one character is transmitted on the slave side (step 509), a delimiter reception determination is performed (step 510), and only when a delimiter is received can the next delimiter be transmitted. This is because the process shifts to a reception standby state (step 513).

In this way, when the transmission timer interrupt occurs, the main station M
If the master station is in the process of transmitting or receiving, by sending a delimiter from the master station side, the slave station that is currently communicating can be placed in a dormant state until the next delimiter is sent.

Then, at the end of the transmission timer interrupt, the master station transmits the delimiter again (step 409), thereby canceling the dormant state (step 512 or 513). The transmission or reception operation will be restarted from this state.

By executing the control programs shown in the flowcharts of FIGS. 3 to 5, the master station M sends the slave stations S2 to S6 in a fixed order after each communication ends, as shown in the time chart of FIG. While cyclically accessing and communicating, it is possible to interrupt the current communication operation by sending a delimiter from the main station at regular intervals, and access the priority station and communicate during that time. be.

Therefore, according to the system of the present invention, data is transmitted cyclically to the slave stations 82 to S6 with equal delay times, while data is transmitted to the priority station S1 at a higher speed and with a certain delay time. It is possible to do this.

It goes without saying that the present invention can be widely applied to general data transmission in addition to the remote I10 base unit and remote I10 unit of the programmable controller.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the connection state of each station in the system of the present invention, Fig. 2 is a block diagram showing the hardware configuration of the master station and slave stations, and Fig. 3 is a block diagram showing the connection state of each station in the system of the present invention. FIG. 4 is a flowchart showing a control program for click transmission/reception processing, FIG. 4 is a flowchart showing a control program for scheduled transmission/reception processing performed by the master station, FIG. 5 is a flowchart showing a control program for transmission/reception processing performed by a slave station, and FIG. FIG. 7 is a time chart systematically showing the transmission and reception procedure in the system of the present invention, and is an explanatory diagram showing the structure of the transmission and reception data. M・・・・・・・・・・・・・・・Main station S,・・・・・・
...Priority station 82-S6...Slave station

Claims (1)

[Claims] (1) While the master station cyclically accesses and communicates with each slave station (excluding the priority station) in a fixed order after waiting for the end of each communication, the master station sends a delimiter at a fixed time interval to perform communication at that point. A cyclic transmission system characterized by interrupting communication operations during which communication is being performed, and accessing and communicating with a priority station during that time.