Siemens SIMATIC FM 353 Manual page 113

As soon as a Write request is detected (also on a signal change in the case of
single functions), it is serviced immediately upon completion of the transfer cur-
rently in progress, if any. Be sure that signals for single commands are not set
cyclically, as this could prevent other job requests from being serviced (priority).
Order/priority of Write requests:
1. Write single commands
2. Write single functions
3. Write requests.
The Write requests are serviced in the order of the Initiate signals,
which is stipulated in user data block AW-DB (from DBX38.0 to 39.7).
Order/priority of Read requests:
1. Read error code, operator/traverse errors or data errors
2. Read requests
The Read requests are serviced in the order of the Initiate signals,
which is stipulated in user data block AW-DB (from DBX42.0 to 43.6).
S Job request status
You can read the status of the job processing infrom the RETVAL instance
variable of the block and from the "Write/read job in progress" signals in user
data block AW-DB (DBX68.0 and DBX68.2). You can evaluate the status of an
individual job request by evaluating the Initiate, Ready and Error signals for that
job request.
Table 6-7 Job request status
Job request status
1. Job in progress
2. Job completed without
errors
3. Write job completed with
errors in this job
4. Write job aborted or not
executed
5. Read job aborted
6. Write and Read aborted
or not executed (in case
of simultaneous job re-
quests)
− Irrelevant for error evaluation
FM 353 Stepper Drive Positioning Module
6ES7 353-1AH01-8BG0
RETVAL Jobs in
instance progress
variable (DBX68.0
(integer) DBX68.2)
1 1
0 −
−1 −
−1 −
−2 −
−3 −
Programming the Technological Functions
Initiate Ready
signals signals
(DBB34...43) (DBB44...53)
1 −
− 1
− 1
− −
− −
− −
Error
signals
(DBB54...63)
−
−
1
1
1
1
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