Sequence Of Communication - BONFIGLIOLI Vectron Agile Series Communications Manual

Handling of the Objects
16.1.5

Sequence of Communication

A request from the master is always answered with a reply from the slave. Each PPO can only accept
one request or one reply at a time. In this way, a defined hand-shake procedure between master and
slave must be complied with.
In the initial situation, the request and reply identification must = 0. The master sets its request
identification and waits for the slave to change the reply identification from 0 to ≠ 0. Now, the reply
from the slave is available and can be evaluated. Thereupon, the master sets its request identification
= 0 and waits for the slave to change the reply identification from ≠ 0 to 0. With this, the
communication cycle is completed and a new one can start.
Attention! The slave only replies to new requests if it has reacted to the request identification = 0
with the reply identification = 0.
28 Profibus DP V1 Agile 06/2010