Technical data

3.3.2.2 Cyclic I/Os (ZP), only with CP 5430 TF
The demanding requirements of cyclic communication for automation
functions of a field device cannot be met by direct HDB calls. Instead of
cyclic HDB calls, the CP 5430 TF also provides the POLL or cyclic I/Os
service.
The term "cyclic I/Os" means that part of the I/O area is not used by I/O
modules, but rather for cyclic data exchange between SIMATIC
programmable controllers and passive stations. "Cyclic data exchange"
involves the CP 5430 TF transmitting the entire output area assigned to the
cyclic I/Os and updating the entire input area assigned to the cyclic I/Os
with the received data cyclically. The cyclic I/O area is in the I/O area of the
controller and is also used by the PLC program. The address areas are
processed with STEP 5 operations. The mode can either be synchronized
with the cycle or free. With the cycle-synchronized mode, a CP-HDB must
be called at the checkpoints required by the user to ensure the consistency
of inputs and outputs. This HDB also triggers a group job for data
transmission.
ZP data transmission is suitable for communication between SIMATIC S5
PLCs and field devices. Field devices are passive stations which cannot
access the bus themselves and must then be constantly or cyclically polled
by active L2 stations.
The CP 5430 TF uses the SRD transmission service to send data to the
slave stations on the SINEC L2 bus.
The basic procedure for this communication is described in Chapter 10
B8976060/02 Fundamentals of the Model
3 - 17 Volume 1