Table of Contents
Advertisement
You should therefore evaluate the DONE and ERROR parameters at each block call. If the
transfer was successful, DONE = TRUE is set. This, however, only means that the transfer
between the reader and the FB (CPU) was error-free. To find out whether the DMC
evaluation was successful, you will need to evaluate bits READ (bit 3), MATCH (bit 4) and
N_OK (bit 5) in the status byte of the reader. You fill find the reactions of FB79 in the
following table. You should also evaluate ERRCODE to learn of warnings from the FB.
Reader
The code could not be decoded.
The code was successfully decoded;
however, you have not set any
specifications.
The code was successfully decoded but
does not match your specifications.
The code was successfully decoded and
matches your specifications.
Process the data entered in RECV before the next trigger otherwise there is no guarantee of
the consistency of this data! At the same time, you should also evaluate the LENGTH
parameter, since the receive area is written only up to this length.
You can cancel a current read job by calling FB79 with COMMAND = W#16#0000.
If an error occurs when processing a job or when a current read job is canceled, ERROR =
TRUE is set. In this case, the ERRCODE parameter contains an ID indicating the cause of
the error. FB79 writes B#16#00 to the RECV target area.
Startup behavior
If an error occurs (ERRCODE <> DW#16#0000 0000), you will need to initialize the FB once
with RESET=TRUE after calling an interrupt OB (for example OB82) and after a STOP-RUN
change on the CPU. Please include a suitable first call in your user program.
SIMATIC MV420 / SIMATIC MV440
Operating Instructions, 04/2013, A5E02371045-06
Process interfacing via an automation system (PLC, PC)
Target area RECV
FB79 enters the string set in "ReadErr".
FB79 enters the result string.
FB79 enters the string set in "MatchErr" or "FilterMsg" if the match or filter
function is selected in the parameter settings. If both of these functions are
selected, FB79 enters the string set in "MatchErr". For more detailed
information on "MatchErr" and "FilterMsg", refer to chapter 5.
FB79 enters the result string.
10.4 Control with FB79
291
Advertisement
Table of Contents
