Technical data

5.4 Data Transmission with Cyclic I/Os (ZP)
(CP 5430 TF)
Data transmission with cyclic I/Os is suitable for communication between
SIMATIC S5 PLCs and PROFIBUS compatible field devices. The field
devices are passive stations that cannot access the bus themselves and
must normally be polled cyclically by active L2 stations.
The "cyclic I/Os (ZP)" type of data transmission is easy to use, i.e. far less
programming is required compared with the other types of data
transmission, for example the "free layer 2 access" (Chapter 8).
This type of communication has the following characteristics:
➣ The data transmission takes one of the two following forms:
– synchronized with the cycle, triggered by the PLC program using
the I/Os (the PLC determines when the data transmission takes
place)
or
– free, initiated by the CP using the I/Os (the CP determines when
the data transmission takes place).
➣ The station relationship is a 1 : 1 relationship:
station (PLC<->CP) <-----> station
➣ The data structures to be transmitted are related blocks of data of 1 to
242 bytes.
Special features:
With this type of communication, the base interface is always used.
B8976060/02 Selecting the Type of Communication
5 - 7 Volume 1