Siemens SIMATIC MV500 Operating Instructions Manual page 185

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 224)").
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.
When a new job is started, the output parameters are reset.
Note
Multiple calls of FB 79 with the same instance is not permitted
Note that making multiple calls of FB 79 with the same instance is not permitted
Note that you can use the parameters in the "Settings > Communication > Use" menu of the
WBM to influence the sequence of command execution of the function block:
• If you want to read out a result string using the function block, the output of the result
string must be set to PROFINET IO. With the jobs "Select program" (COMMAND
SIMATIC MV500
Operating Instructions, 03/2021, C79000-G8976-C494-05
Process interfacing via an automation system (PLC, PC)
9.4 Control with FB 79
185