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Process interfacing via an automation system (PLC, PC)
9.4 Control with FB 79
Functional scope of FB 79
Note that the function block only monitors the pure data traffic between the optical reader
and the controller. This means that the "DONE" parameter does not allow any conclusion to
be made on the actual read result. To obtain a good/bad read evaluation, you need to
process the following result bits of the status byte:
● READ
● MATCH
● NOK
The following bits of the control byte must be edited outside the function block:
● TRG (Trigger)
Start processing
● RES (Reset)
Acknowledgment of an error (see section "Error messages (Page 176)").
The following commands can be executed with FB 79:
● Cancel current job.
● Select program.
● Save a program.
● Output the result strings.
● Output the position of the code.
● Output the quality characteristics of the currently read code.
● Output the number of the currently selected program.
● Output the current operating state of the optical reader.
● Reset the "DISA" control signal.
Whether or not a job can be executed successfully depends on the current operating state of
the optical reader and its parameter settings. A description of which jobs are possible in
which operating states of the optical reader is provided below.
The FB 79 sets the "DISA" control signal on the optical reader to "TRUE" for almost all jobs.
This is intended to prevent the optical reader being controlled from an additional HMI device
at the same time. This does not apply to the following four commands:
● Reset the "DISA" control signal.
● Cancel current job. The "DISA" function block does not change with this.
● Output the number of the currently selected program. The "DISA" function block does not
change with this.
● Output the current operating state of the optical reader. The "DISA" function block does
not change with this.
140
Operating Instructions, 05/2019, C79000-G8976-C494-02
SIMATIC MV500
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