JPH06243012A - Control method for file in distributed system - Google Patents

Abstract

PURPOSE:To guarantee the data alteration by a user on simultaneous access to the same file. CONSTITUTION:The control method of the file in a process monitor controlling system where a programmable controller and MMI (CRT monitor input devices) are connected by a communication line and plural CRT monitor input devices which one programmable controller manages asynchronously read/write data is provided with alteration flags for respective blocks obtained by dividing one file into plural blocks. Only data of the alteration block and the alteration flag of MMI are transmitted to the programmable controller. When the alteration flag of a master file and the alteration flag transmitted from MMI are not duplicated, writing is permitted. When they are duplicated, writing is rejected. The number of MMI which can simultaneously be assessable to the same file is set, and the alteration flag is reset when the number of MMI in the middle of access becomes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a file access between a programmable controller and a CRT monitoring input device installed at a manufacturing site such as a steel plant, a chemical plant, a papermaking plant, etc. File control method.

[0002]

2. Description of the Related Art A conventional file access method between a programmable controller (hereinafter referred to as PLC) and a CRT monitoring input device (hereinafter referred to as MMI) is a master file 804 stored in a PLC 801 as shown in FIG. (A) 802, MMI (B) 803 read out via the communication line, and copy files 805, 8 respectively.
It is retained as 06. That is, the same file may be simultaneously accessed by a plurality of MMIs.
In such a case, when the MMI (A) writes the file contents modified before the MMI (B) to the PLC, the changed contents are reflected in the PLC, and the process according to the changed contents is performed. However, after that, the MMI (B) changes the file contents different from the contents changed by the MMI (A), and P
When a file is written to the LC, the changes made by the MMI (A) are erased instead of being reflected by the changes made by the MMI (B).

[0003]

In the prior art, it is left to the user to manage files so that such a problem does not occur, and the MMI for the PLC is left to the user.
There was a problem that important data changes etc. were not guaranteed. Therefore, an object of the present invention is to guarantee the user's data change regarding the above-mentioned simultaneous access to the same file.

[0004]

Therefore, in order to solve the above-mentioned problems, the present invention has a programmable controller and an MM.
I (CRT monitoring input device) is connected by a communication line, and a file is controlled by a plurality of CRT monitoring input devices asynchronously reading and writing a file managed by one programmable controller. A change flag is provided for each block divided into a plurality of blocks, and only the data of the changed block and the change flag of the MMI are sent to the programmable controller when writing a file, and the change flag of the master file and the change flag transmitted from the MMI are duplicated. If not, write is permitted. If duplicate, write is denied. Furthermore, the number of MMIs that can access the same file at the same time is set. I tried to reset it.

[0005]

With the above means, first, for any same block of one master file in the PLC, the MMI is first set.
When (A) writes, the change flag in the master file turns on, and when MMI (B) tries to write,
Writing is rejected because the change flag in the master file is already on. As a result, the data written by MMI (A) is guaranteed.

[0006]

EXAMPLES Specific examples of the present invention will be described below. FIG. 1 is a system configuration diagram of a process monitoring and control system including one PLC and three MMIs. PL
Although there are a plurality of files in C, an example of one of the files is a file 112 that stores control parameters for a device. There are four types of control parameters (a) to (d) in this, and the blocks (1) to (4) corresponding to them are 11
It is divided into 4 to 117 and recorded. Reference numeral 113 is a flag group used for managing the writing of data in each block, and each flag 118 to 121 is each block (1) to
It corresponds to (4). The state of the flag is 0, which means that the block data has not changed, and 1 means that the data in the block has changed. Here, copy 1 of the master file 112
02, 105 and 108 are MMIs (A), (B),
MMI as stored in (C)
The case where the control parameter (b) in (A), the control parameter (c) in MMI (B), and the control parameters (b) and (d) in MMI (C) are changed by each operator will be described. As a specific example, three M files are stored for one master file 112 stored in the PLC 111.
Consider a case where a file is read, data is changed, and data is written from the MI at the same time. A case in which the block (2) 103 is changed in the MMI (A) 101, the block (3) 106 is changed in the MMI (B) 104, and the block (2) 109 and the block (4) 110 are changed in the MMI (C) 107 will be described. . The block data changed by the MMI is transmitted to the PLC via the communication line, but the transmission content may be only the changed block data and flag data. First, in the MMI (A), when the block (2) 103 of the copy file 102 is changed and a master file change request is issued to the PLC, the data 115 of the block (2) in the master file is changed and changed. The flag 119 is set. Next, when there is a change request for the block (3) 106 from the MMI (B), the data 115 of the block (3) of the master file 112 in the PLC is changed and the change flag 120 is set. Furthermore M
Block (2) 109 and block (4) from MI (C)
When there is a change request for 110, it tries to write the block data 109 of the copy file to the block (2) of the master file 112 in the PLC, but since the change flag 119 has already been set to 1 (data change), the flag Are duplicated and writing is rejected. But,
Change flag 1 for data 110 of block (4)
Since 21 is a state of 0 (no data change), the flags do not overlap, the writing is accepted, the data 117 is changed, and the change flag 121 is set to 1. That is, in the MMI (C), the change of the block (2) is rejected because the MMI (A) changed the data first, but the change of the block (4) is accepted because the data has not been changed by any MMI. It The write operation and the process of changing the change flag in this example will be described in detail.
First, in the initial state, neither the PLC change flag nor each MMI change flag is set (state of "0000").
I shall. Block (2) in MMI (A)
Block (3) is changed in (B), and first MMI (A)
The change flag “0010” transmitted from the server is compared with the change flag “0000” of the master file. In this case, since the bit of block (2) in the change flag of the master file is 0 (no change), the flags do not overlap, and the write request from this MMI (A) is accepted. As a result, the change flag in the master file is "001
The state becomes "0". Next, when a write request is received from the MMI (B), the change flag "0100" is compared with the change flag "0010" of the master file. In this case as well, since the change flags do not overlap, MMI (B)
The write request is accepted, and as a result, the change flag in the master file becomes the state of "0110". Then M
When blocks (2) and (4) are changed in MI (C),
The write request from the MMI (C) indicates that the change flag is “10.
As a result of comparison between “10” and the change flag “0110” of the master file, writing is rejected for block (2) because the flags are duplicated. However, since the flag is 0 for block (4), writing is accepted. As a result, the change flag in the master file is "1.
110 ”. FIG. 2 is a diagram for explaining the method of resetting the change flag, and shows an operating condition when the maximum number of simultaneously accessible MMIs for the same file is set to three. MMI for one master file
When (A), MMI (B), and MMI (C) access in order, the maximum number of accessible units is 3 when the access 203 of MMI (C) is accepted, so the next MMI (D)
Access 204 is denied. Then MMI (A),
Access of MMI (C) is completed, and finally MMI (B)
At the end of access 207, the change flag is reset (“0
000 ”state). The MMI (E) access 205 is accepted because the change flag is reset. In other words, from the access start 201 of MMI (A) to M
Until the MI (B) access end 207, access from the fourth unit onward is denied. FIG. 3 is a diagram showing a file access processing flow. The operation of changing the file data once from the MMI is shown. MMI to P
Four requests are issued to the LC, and PL is issued to them.
In C, each request is processed and a response is returned to the MMI. Each processing of 301, 302, 303, 304 is PLC
This is the processing on the side, the details of which are shown in FIGS.
The process 401 (FIG. 4) is a file access start process (O
Pen) and check the number of currently accessed units 411
And obtain access right 412. A process 402 (FIG. 5) is a file reading process (Read), which includes an access right check 413 and a reading process 414. A process 403 (FIG. 6) is a file write process, and includes access right check 415, change flag check 416, write process 417, and change flag update 41.
Perform 8. A process 404 (FIG. 7) is a file access end process (CLOSE), which is performed by checking the number of currently accessed devices 419 and resetting the change flag 420.

[0007]

As described above, according to the present invention, P
Multiple MMI for one master file in LC
When the user tries to access, even if the change contents of the same file are different for each MMI, if the change blocks in the file do not overlap, the change contents are all P
Since it can be reflected in the master file in the LC, there is an effect that the contents of changes made by the user in each MMI are guaranteed. Further, the block data changed by the MMI is transmitted to the PLC via the communication line, but since the transmission contents need only the changed block data and flag data, compared to the conventional method of always transmitting / receiving the entire file. Since the transmitted and received data is compressed, efficient transmission is possible.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a change duplication check method of the present invention.

FIG. 2 is a diagram showing a method of resetting a change flag.

FIG. 3 is a diagram showing a file access processing flow.

FIG. 4 is a diagram showing a processing flow on the PLC side of FIG. 3;

5 is a diagram showing a processing flow on the PLC side of FIG. 3;

FIG. 8 is a diagram showing a conventional technique.

[Explanation of symbols]

101, 104, 107 CRT monitoring input device (MM
I) 111 programmable controller (PLC) 112 master file in PLC 102, 105, 108 copy file in MMI 401 file access start processing flow 402 file reading processing flow 403 file writing processing flow 404 file access end processing flow 411 to 420 detailed processing Item 801 PLC 802, 803 MMI

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[Procedure amendment]

[Submission date] December 21, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a diagram for explaining a change duplication check method of the present invention.

FIG. 2 is a diagram showing a method of resetting a change flag.

FIG. 3 is a diagram showing a file access processing flow.

FIG. 4 is a diagram showing a processing flow on the PLC side of FIG. 3;

5 is a diagram showing a processing flow on the PLC side of FIG. 3;

FIG. 6 is a diagram showing a processing flow on the PLC side of FIG. 3;

FIG. 7 is a diagram showing a processing flow on the PLC side of FIG. 3;

FIG. 8 is a diagram showing a conventional technique.

[Explanation of Codes] 101, 104, 107 CRT monitoring input device (MM
I) 111 programmable controller (PLC) 112 master file in PLC 102, 105, 108 copy file in MMI 401 file access start processing flow 402 file reading processing flow 403 file writing processing flow 404 file access end processing flow 411 to 420 detailed processing Item 801 PLC 802, 803 MMI

Claims (1)

[Claims] 1. A file control method in a process monitoring control system, wherein a programmable controller and a CRT monitoring input device are connected by a communication line, and a plurality of CRT monitoring input devices asynchronously read and write files managed by one programmable controller. A change flag is provided for each block obtained by dividing one file into a plurality of blocks, and when writing the file, only the change block data and the change flag of the CRT monitoring input device are sent to the programmable controller to change the master file and the CRT monitoring input. If the change flag sent from the device does not overlap, write is permitted, if it is, the write is rejected, and the number of CRT monitoring input devices that can simultaneously access the same file is set. , Accessing A file control method in a distributed system, characterized in that a change flag is reset when the number of vehicles becomes 0.