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Siemens SIMATIC MV540 H - Example Program for Data Exchange if Code Length ≤ 27 Bytes

Siemens SIMATIC MV540 H
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Process interfacing via an automation system (PLC, PC)
9.4 Control with FB 79
SIMATIC MV500
136 Operating Instructions, 06/2018, C79000-G8976-C494-01
Start processing
Processing starts immediately on completion of the program saving.
Table 9- 41 Processing of program memory
Step
Input
Output
Description
1
You select a program, for example, program 11.
2
READ
MATCH
N_OK
The outputs are set as follows depending on the processing re-
sult:
Code was localized and decoded.
Code matches the trained code.
Code was not legible.
9.4.3
Example program for data exchange if code length ≤ 27 bytes
Below, you can find an example program for data exchange when the code length is a
maximum of 27 bytes.
Note
Compatible S7 controllers
The example program can only run on the following S7 controllers:
On a CPU 318 and all S7-400 CPUs.
On all S7-300 CPUs with MMC
On all other S7
-300 and S7-400 CPUs, you must use SFCs 14 and 15 for all access to the
two user data interfaces.
Explanation of the program
The example program has the following properties:
Only the pure result string with data ID "B#16#81" is output.
The I/O controller does not check how many bytes the optical reader has returned but
always reads 27 bytes.
The I/O controller does not monitor anything.
The start of the "Send" user data interface is at address 4 of the process image input.
The start of the "Receive" user data interface is at address 4 of the process image output.
To ensure the consistency over the entire area of 32 bytes, there must be no update of
the process image during the program shown here.
The user data is stored in data block DB17 starting at byte 4.

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