Festo Кабели и принадлежности - Manual (Page 108)

5. Parameter channel
5−8
Festo P.BE−SPC200−COM−PDP−E N en 0901c
5.2.2 Rules for task reply processing
Rules Description
1 If the master sends the identifier for No task," the SPC200 responds with the reply
identifier for No reply."
2 A task or reply telegram always refers to an individual parameter.
3 The master must continue to send a task until it has received the appropriate reply from
the SPC200.
4 The master recognizes the reply to the task placed:
Ĉ by evaluating the reply identifier
Ĉ by evaluating the parameter number (PNU)
Ĉ if applicable, by evaluating the subindex (IND)
Ĉ if applicable, by evaluating the parameter value.
5 The SPC200 supplies the reply until the master sends a new task.
6 With reply telegrams to the tasks Request parameter value" and Request parameter
value (array)," the SPC200 always replies with the current value.
7 a) A write task, even with cyclic repetition of the same task, will only be carried out once
by the SPC200.
b) Between two consecutive tasks with the same task identifier (AK), parameter number
(PNU) and subindex (IND), the task identifier 0 (no task) must be sent and the reply
identifier 0 (no reply) must be expected. This is to ensure that an old" reply is not
interpreted as a new" reply.
Sequence of parameter processing
The master transmits a task to the SPC200 and repeats this
task until the appropriate reply is received.
a parameter modification in the SPC200 is only reliably effecĆ
tive if the reply telegram contains the appropriate reply identĆ
ifier for the parameter number (PNU) and, if applicable, for
the subindex (IND).