JPH0695718A - Remote i/o system for programmable controller - Google Patents

Abstract

PURPOSE:To shorten the polling cycle time and to increase the data exchange speed between a master station and a slave station. CONSTITUTION:When output data to be transmitted to a slave station 3 is not changed from output data for preceding polling, a master station does not set a transmission command neither output data to a polling frame and sets only a reception command to transmit the polling frame to the slave station 3. The slave station 3 receives this polling frame; and when input data which have been fetched through an input unit 3a and should be returned to the master station 2, is not changed from input data for preceding polling, the slave station 3 does not set input data and returns a response frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a remote I / O of a PC comprising a master station connected to a programmable controller (hereinafter referred to as a PC) and a small station connected to the master station.
Regarding the O system.

[0002]

2. Description of the Related Art When controlling a plurality of devices dispersed in a factory or the like with a single PC, it is necessary to connect several tens of input / output wires from the PC to each device, which makes wiring work complicated. And problems such as increased installation work will occur. In order to solve this problem, a PC remote I / O system configured as shown in FIG. 8 was devised for the purpose of wire saving.

The remote I / O system of a PC is a CPU
A master station 2 that is incorporated in a PC in the same manner as the unit (hereinafter referred to as a PC main body) 1 and the input / output units (I / O units) 1a and 1b, and is directly connected to the PC main body 1 and the like via a CPU bus, The master station 2 and one or a plurality of small stations 3 connected via a communication cable 4 such as a coaxial cable or an optical fiber.

Each small station 3 is usually connected to a plurality of input / output units 3a and 3b via a data bus, and a motor and a switch (S) are connected to each input / output unit 3a and 3b.
W), a controlled device such as a sensor are connected, and the PC body 1 is configured to control a remote non-controlled device.

The remote I / O of the PC configured as described above
In the O system, when the PC main body 1 controls the input / output units 3a and 3b on the small station 3 via the master station 2, the input data on the small station 3 is transferred to the PC main body 1 via the master station 2 to the PC main body 1 Output data of the output unit 3b on the small station 3 via the master station 2
Need to output to.

Here, the data communication method between the PC body 1 and the present system includes a method for executing instruction execution and communication processing in synchronization with execution of a remote input / output instruction in a command word of the PC body, and a fixed time or There is a method of asynchronously performing the end refresh timing, which is called remote refresh processing.

Data transmission / reception between a master station and a small station is usually performed by polling / selection by the master station, that is, a polling frame in which output data is set in the order of node numbers is sent to each small station, and the polling frame is transmitted. This is performed by the receiving small station setting the input data in the response frame and returning it to the parent station.

[0008]

By the way, in such a conventional remote I / O system, a polling frame is sequentially transmitted to each small station, output data is transmitted for each small station, and input data is received. As a result, the polling cycle time becomes long, data cannot be exchanged at high speed between the master station and the small station, which affects the instruction execution time of the PC main unit and the I / O unit connected to the small station. Has the problem that it cannot be accessed like the I / O unit on the PC body.

Therefore, the present invention has been made to solve the above problem, and provides a remote I / O system for a PC which can shorten the polling cycle time and speed up data exchange between a master station and a small station. The purpose is to do.

[0010]

To achieve the above object, according to the present invention, a master station directly connected to a PC main body, a master station connected to the master station via a communication cable, and a plurality of input units are connected. The master station transmits the output data from the PC body to each small station by the polling / selection method, and receives the input data captured by each small station via the input unit. In a remote I / O system of a programmable controller in which the PC body can refresh input / output data, the master station has an output data memory for storing output data to be transmitted from the PC body to a small station,
Output change flag that compares the output data stored in the output data memory with the output data sent to the small station at the time of the previous polling, and sets the output change flag if the data value has changed. The output change flag is set by the setting means and the output change flag setting means, and if the output change flag is not set, the output data stored in the output data memory is set in the polling frame. On the other hand, when the output change flag is set, the polling means for transmitting the output data without setting it in the polling frame is provided, while the small station inputs the data received through the input unit. Input data memory to store data, input data stored in the above input data memory, and returned at the last polling The input data is compared with the force data, and if the value of the data is changing, it is determined whether or not the input change flag is set by the input change flag setting means for setting the input change flag and the input change flag setting means. do it,
When the input change flag is not set, the input data stored in the input data memory is set in the response frame and returned, while when the input change flag is set, the input data is set in the response frame. It is characterized by comprising a response means for returning without doing.

[0011]

In the present invention, the master station compares the output data, which is stored in the output data memory and should be transmitted from the PC body to the small station this time, with the stored output data transmitted at the previous polling. , If the data value has changed, set the output data in the polling frame and send it. If the data value has not changed, send the output data without setting it in the polling frame. .

At the small station, if the input data stored through the input unit and stored in the input data memory is compared with the stored input data returned at the previous polling, the value of the data has changed. Only, the input data is set in the response frame and returned, and when the data value does not change, the input data is returned without being set in the response frame.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a PC remote I / O system according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the remote I / O of the PC of this embodiment.
The system configuration is shown.

This system is built into a PC in the same manner as the PC body 1 and the input / output unit (see FIG. 8).
And the like, and one or a plurality of units connected to the master station 2 via a communication cable 4 such as a coaxial communication cable or an optical fiber (one unit for convenience in this figure). (Only shown).

The PC main body 1 controls a machine or device such as a motor through an input / output unit (see FIG. 8) directly incorporated in the PC and input / output units 3a and 3b connected to the present system. In this figure, only the MPU 11 that executes communication with the system, that is, remote refresh is shown.

The master station 2 transmits / receives data to / from the PC body 1 via the CPU bus, and controls communication by polling / selection with the small station 3 via the communication cable 4 as output change flag setting means and polling means. The MPU 21 has a shared RAM 22 that exchanges output data and input data with the PC body 1, and a communication LSI 23 that incorporates a transmission / reception buffer (not shown) and that communicates with the small station 3. Incidentally, Ao is a remote refresh request signal for requesting the master station 2 to write and read input / output data to the PC body 1, and A1 is transmitted from the PC body 1 to the master station 2 when the access to the shared RAM 22 is completed. This is a remote refresh completion signal.

The small station 3 functions as an input change flag setting means and a response means via the communication cable 4 to control communication with the master station 2 and data transmission / reception with the input / output units 3a and 3b, and a transmission / reception buffer (not shown). No)
It has a communication LSI 32 that has a built-in device and communicates with the master station 2, and an input data memory 33 that captures the value of an input pulse input via the input unit 3a and stores it as input data.

FIG. 2 shows a detailed structure of a polling frame or a response frame transmitted / received between the master station 2 and the small station 3.

This communication frame includes, for example, a preamble (P) of about 1 byte and a synchronous character (S).
YN), address (ADRS), control field (CNF), and frame check sequence (FCS) of about 2 bytes, and data (DATA) of about several tens to 1000 bytes. Then, in the case of the polling frame, the control field (CN
In F), a transmission command for instructing the small station to fetch the output data and a reception command for instructing the setting of the input data are set in the response.

3 (a) and 3 (b) show the setting procedure of the input change flag and the output change flag, respectively.

(A) shows an example of setting the input change flag in the MPU 31 of the small station 3. The MPU 31 receives the polling frame from the master station 2 and the input data "00101101" of this time, and Input data “0000” returned by the previous polling stored in
1101 ", and when the data value is different between the previous time and this time, that is, when the input data is changed,
While the input change flag is set to "1", if the input data has not changed, the input change flag is set to "0" and held in a register or the like.

In the same way as above, the MPU 21 of the master station 2, as shown in FIG.
The output data “10010101” to be transmitted to the small station 3 is compared with the output data “11010101” stored in the previous station stored at the time of the previous polling.
When the output data has changed, the output change flag is set to "1", while when the output data has not changed, the output change flag is set to "0" and held in the register.

Next, the operation of the present system thus constructed will be described.

FIG. 4 shows the procedure of polling / selection communication processing in the master station 2.

In this figure, the communication process between the master station 2 and the three small stations A to C is shown, and particularly the communication process with the small station A (step 100) is shown in detail.

First, in this process, a predetermined communication start process with the small station A is performed (step 110), and an output change flag indicating a change in the output data to the small station A stored in the above-mentioned register or the like is set. If it is determined (step 120) and the output change flag is set to "1" (step 120 "Yes"), the output data to be transmitted to the small station A at the time of this polling is the same at the time of the previous polling. Since it indicates that the output data is different from the output data transmitted to the small station A, as shown in FIG. 2, the transmission command and the reception command are set in the control field (CNF) of the polling frame, and the output is sent to the polling frame. Data is set and transmitted to the small station A (step 13)
0).

On the other hand, when the output change flag is "0" (step 120 "No"), the output data to be transmitted to the small station A this time is different from the output data transmitted to the small station A at the time of the previous polling. Therefore, the output data is not set in the polling frame, and only the reception command is set in the control field (CNF) of this polling frame and transmitted (step 140).

Therefore, in the master station 2, when the output data to be transmitted to the small station A is not different from the output data transmitted last time, the master station 2 does not transmit the output data, and therefore only that data is transmitted. The polling frame is shortened and the polling time is shortened.

Although not shown here, the small station A fetches and stores the input data, compares the input data with the input data returned at the previous polling, and shows the comparison result. Input change flag is set.

When the polling frame from the master station 2 is received, first, if there is a transmission command in the control field (CNF), the output data is taken in according to the transmission command, while if there is no transmission command, the output data is output. Do not import.

Further, when the input change flag stored in the register or the like is judged according to the received command of the control field (CNF) and "1" is set in the input change flag, that is, the current input data and the previous polling time are set. If the input data returned is different, substation A
Sets the input data in the response frame and the master station 2
Return to. On the other hand, when the input change flag is "0", the small station A returns the response frame to the master station 2 without setting the input data.

For this reason, in the master station 2, when the input change flag is set to "1" in the small station A (step 150 "Yes"), when a response frame is returned from the small station A. While receiving the response and the input data (step 160), if the input change flag is not set to "1" in the small station A (step 150).
"No"), only the response is received when the response frame is returned from the small station A (step 17).
0), followed by terminating the communication process with the small station A (step 180).

Therefore, in the small station A, if the input data to be returned to the master station 2 is not different from the input data returned at the time of the previous polling, the input data is not returned, and therefore only that data is returned. The response frame is shortened and the polling time is also shortened.

After the communication processing with the small station A is completed,
The other two small stations B and C perform communication processing in the same manner as in the case of small station A (steps 200 and 300), and when the processing is completed, return to communication processing with small station A (step 100).

Next, how much the communication cycle time is shortened by the present system as compared with the conventional system will be described.
And communication between the three small stations A to C will be described as an example. First, FIG. 5 shows the conditions of the output change flag and the input change flag for each of the small stations A to C. That is, for the small station A, there is output data transmitted from the master station 2,
Moreover, the condition that there is input data to be returned to the master station 2, such input / output data for the small station B, and only input data to be returned to the master station for the small station C is shown. There is.

When data communication is executed by this system under such conditions, the frame to be communicated and one communication cycle time are as shown in FIG.
In FIG. 7 and FIG. 7, which will be described next, responses such as preamble (P) and synchronous character (SYN) related to commands other than commands and data are omitted.

That is, first, in the frame communicated between the master station 2 and the small station A, since the output change flag and the input change flag are set to "1" (see FIG. 5), the transmission command, It consists of output (OUT) data, a received command, and an input (IN) command. Here, the communication time in which those frames are combined is Ta.

In the frame communicated with the small station B, since both the output change flag and the input change flag remain "0" (see FIG. 5), only the receive command is transmitted from the master station. , No output data is sent, and
Since the input data is not returned, only the receive command is available. Therefore, the communication time for the small station B is the communication time Tb for only the received command.

Further, in the frame communicated with the small station C, the output change flag is not set to "1" and the input change flag is set to "1" (see FIG. 5). From the master station, only the received command is set in the polling frame and transmitted, and the input data is set in the response frame and returned. Therefore, small station 3
The communication time required for is the total time Tc of the received command and the input data.

On the other hand, such a condition (see FIG. 5)
When communication is performed by the conventional remote I / O system, the result is as shown in FIG. That is, according to the conventional system, each of the small stations A to C transmits the frame of the transmission command, the output data, the reception command, and the input data regardless of the values of the output change flag and the input change flag.

Therefore, one communication cycle time T = Ta + Tb + Tc according to the present system and 1 according to the conventional system.
Communication cycle time T '= Ta' (Ta) + Tb '+ T
As is clear from comparison with c ', in this system, when the output data to be transmitted to the small station is the same as the output data at the time of the previous polling, and the input data to be returned to the master station is at the time of the previous polling. If the input data is the same as the input data of No. 2, the output data and the input data of several tens to several 1000 bytes, which occupy most of the communication frame, are not transmitted as described with reference to FIG. The polling cycle time, that is, the communication cycle time is shortened.

[0043]

As described above, according to the present invention, when the output data to be transmitted to the small station at the master station is not different from the output data at the previous polling time at the small station, the output data is changed. Is not sent, and if the input data to be returned to the parent station in the small station is not different from the input data at the previous polling in the small station, the input data is not sent back. The communication frame is shortened by the amount of data and input data, and the communication cycle time between the master station and the small station is shortened.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a remote I / O system for a PC according to the present invention.

FIG. 2 is an explanatory diagram showing a detailed structure of a communication frame.

FIG. 3A and FIG. 3B are explanatory views showing a procedure for setting input and output change flags, respectively.

FIG. 4 is a flowchart showing a procedure of communication processing in a master station.

FIG. 5 is an explanatory diagram showing conditions of input and output change flags for each of the small stations A to C.

FIG. 6 is an explanatory view showing in simplified form a frame communicated by the present system.

FIG. 7 is an explanatory diagram showing in simplified form a frame communicated by a remote I / O system of a conventional PC.

FIG. 8 is an explanatory diagram showing the configuration of a conventional PC remote I / O system.

[Explanation of symbols]

1 PC Main Body 2 Master Station 3 Small Station 3a Input Unit 4 Communication Cable 21 MPU (Output Change Flag Setting Means, Polling Sending Means) 23 Shared RAM (Output Data Memory) 31 MPU (Input Change Flag Setting Means, Response Returning Means) 33 Input data memory A to C Small station

Claims (1)

[Claims] 1. A master station which is directly connected to a PC main body, and a small station which is connected to the master station via a communication cable and to which a plurality of input units are connected. The master station is polling / selection. According to the method, the output data from the PC main body is transmitted to each small station, and each small station receives the input data taken in through the input unit so that the PC main body can refresh the input / output data. In the remote I / O system of the controller, the master station stores the output data to be transmitted from the PC body to the small station, the output data memory that stores the output data, the output data stored in the output data memory, and the previous polling time Output that compares the output data sent to the small station and sets the output change flag if the data value changes The change flag setting means and the output change flag setting means determine whether or not the output change flag is set. If the output change flag is not set, the output data stored in the output data memory is polled. While the polling means is provided for transmitting the output data without setting it in the polling frame when the output change flag is set, while the small station captures data via the input unit. The input data memory that stores the input data, the input data stored in the input data memory, and the input data returned at the previous polling are compared, and if the data value changes, the input change The input change flag setting means for setting a flag and the input change flag setting means for setting the input change flag If the input change flag is not set, the input data stored in the input data memory is set in the response frame and returned, while if the input change flag is set, And a response means for returning the input data without setting it in a response frame, the mote I / O system of the programmable controller.