VISOR
®
Communications manual
8 Request sequences
Important recommendations for PLC programmers
1. Follow the sequence of requests
2.
Wait for complete execution of an action before sending the next one. Complete
execution takes place when the image ID changes in the trigger request, or the
corresponding acknowledge bit is set for the other requests.
PLEASE NOTE:
The complete execution of an action cannot be reliably determined based on a
low/high transition at READY, since it is possible for there to be long cycle times
between the PLC and VISOR
®
(e.g., 32 ms) that result in READY never having a low
state.
3. READY should always be high before a trigger request is sent
Accepting / discarding of requests of the control module
1. Request is accepted with an increasing acknowledge bit
2. Request is discarded if the error bit is set.
3. Request is discarded without an error bit and acknowledge bit if the sensor is still
processing the previous request and no acknowledgment has yet been set for it. (i.e. not
following the recommended handshake)
06814859 - 1/24/2019-00 Page 42 EN
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