Process interfacing via an automation system (PLC, PC) 
  9.4 Control with FB 79 
SIMATIC MV500 
Operating Instructions, 06/2018, C79000-G8976-C494-01 
147 
module then queries the program selected now on the optical reader and outputs it via 
the "CODE_OUT" parameter.  
If the program now selected matches the program specified at the "PARAM1" parameter, 
the "ACTIVE" parameter has the value "FALSE" and the "DONE" parameter the value 
"TRUE". If the program now selected does not match the program specified at the 
"PARAM1" parameter, the "ACTIVE" parameter has the value "FALSE" and the "ERROR" 
parameter the value "TRUE". The "ERRCODE" parameter contains an appropriate error 
message. The system also checks whether the program change is being blocked by a 
"Service" or "User1" user logged on in the WBM who has taken control of the optical 
reader, and whether the newly selected program has been saved.  
If an error is detected, the "ACTIVE" parameter has the value "FALSE" and the "ERROR" 
parameter has the value "TRUE". The "ERRCODE" parameter contains an appropriate 
error message. 
3.  Call FB 79 again cyclically with "COMMAND=W#16#0081". 
If you attempt to cancel a current change program job, the "ERRCODE" parameter will 
change to "DW#16#00000002"; however, processing for the job will be completed. 
 
Note 
Notes on the program change 
Note the following points when changing programs:
 
  When there is a program change, the optical reader changes to "STOP" for at least 
150 ms. In isolated cases, a program change can take up to 15 s. 
  If you specify the value "0" in the "PARAM1" parameter, the previously selected program 
will be retained. 
  The value of "PARAM1" must not be changed before the job is completed. 
Sequence when saving a program ("COMMAND" = W#16#0002) 
In order for the FB to initiate saving of a code, the "Control" parameter must have the value 
"PROFINET IO" in the "Settings > Communication > Use > Connection" menu of the WBM. 
The job can only be sent when the optical reader does not have the "ERROR" state (see 
also the operating state table following the parameter table). 
When the job is triggered, the parameters "DONE" and "ERROR" have the value "FALSE". 
The "ACTIVE" parameter has the value "TRUE". The block saves the program specified at 
the "PARAM1" parameter. 
 
Note 
Notes on saving 
Note the following points when saving:
 
  In isolated cases, saving a program can take up to 35 s. 
  The value of "PARAM1" must not be changed before the job is completed.