8.1.4 Communication procedure
An order from the master will always be answered by a slave response. Each parameter
request or response can only accept one order/response at a time. For this reason, a
defined handshake procedure must be followed between the master and slave.
In the initial situation, the order and response ID must be = 0. The master sets its order
ID and waits until the slave changes the response ID from 0 to ≠ 0. Now, the slave's
response is available and can be evaluated. Then,
t
he master sets its order ID = 0 and
waits until the slave changes the r
esponse ID from ≠ 0 to 0. This completes the comm
u-
nication cycle and a new cycle can start.
The slave will only respond to new orders once it has reacted to order ID = 0 with re-
sponse ID = 0.
32 CM-PROFINET 10/13
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