Siemens SIMATIC MV440 Operating Instructions Manual page 282

Process interfacing via an automation system (PLC, PC)
10.4 Control with FB79
Description
You will need to process the following bits of the control byte outside the FB:
● TRG (Trigger): Start processing
● RES (Reset): Acknowledge an error (refer to the error messages)
The FB monitors only the data exchange between the reader and the controller, in other
words, the DONE parameter provides no information on the actual read result. To obtain a
good/bad evaluation, you will need to evaluate the following result bits of the status byte:
● READ
● MATCH
● NOK
The following jobs are possible
● Cancel current job
● Select program
● Save a program
● Output 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 mode of the reader
● Reset the DISA control signal
Whether or not a job can execute successfully depends on the current status of the reader
and its parameter settings. Which job can execute in which status of the reader is described
further below.
With almost all jobs, FB79 sets the DISA control signal on the reader to TRUE. This is
intended to prevent the reader being controlled from an HMI device at the same time. The
following four jobs are exceptions:
● Reset the DISA control signal
● Cancel current job. The FB does not change DISA with this.
● Output the number of the currently selected program. The FB does not change DISA with
this.
● Output the current mode of the reader. The FB does not change DISA with this.
When a new job is started, the output parameters are reset.
Note
Multiple FB79 calls with the same instance are not permitted
Multiple FB79 calls with the same instance are not permitted.
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SIMATIC MV420 / SIMATIC MV440
Operating Instructions, 04/2013, A5E02371045-06