Balluff BTL7-T500 Series, Configuration Manual

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4
Configuration (continued)
4.9 Acyclic communication between
a Class-1-Master and a slave (MSAC_C1)
The FDL service SRD and SAP 51 is used for sending
data. The master parameterizes and configures the slave
as for cyclical data communication. Then it can carry out
the previously described acyclic services with the slave in
data communication.
A write request telegram ( Write.req ) is used to initiate
communication. The telegram describes what should
happen (reading or writing a parameter). Processing of this
request in the slave then is started. If the response to the
request is not immediately available, multiple polling cycles
follow until internal processing is finished. The result is
retrieved with the response telegram ( Read.req ).
4.9.1 Telegram Write.req
Write.reg can be used to open a connection and tell the
slave which actions to perform.
When the connection is opened the master starts an
internal timer for communication monitoring. Multiple
polling cycles can occur until the slave provides the
requested data. If the slave does not reply within the set
time, the communication connection is aborted (also for
cyclical data exchange). After the connection is aborted
the slave must be re-parameterized and re-configured. If
the slave replies with an error message, the Class-1-Master
tries the request again.
BTL7-T500-…
Configuration Guide