Technical data

10 Data Transmission with Cyclic I/Os
(CP 5430 TF)
This chapter contains the following information:
➣ The devices and applications for which data transmission with cyclic
I/Os (ZP) is suitable.
➣ How this type of data transmission functions.
➣ How to assign parameters to the CP 5430 TF for this type of data
transmission when an S5 programmable controller is to exchange data
with a field device (example in Section 10.3).
➣ The STEP 5 program for this example.
Applications for data transmission with cyclic I/Os (ZP)
The high, cyclic communications demands for the automation function of a
field device cannot be met with direct HDB calls. Instead of cyclic HDB
calls, the CP 5430 TF therefore provides the cyclic I/Os service.
Data transmission with cyclic I/Os is suitable for communication between
SIMATIC S5 PLCs and field devices. Field devices are passive stations on
the bus which cannot access the bus themselves and must be constantly
(normally cyclically) polled by active L2 stations.
The main feature of data transmission with cyclic I/Os (ZP) is that it is easy
to use, i.e. it involves far less programming compared with other types of
data transmission, for example "free layer 2 access" (refer to Chapter 8).
The term "cyclic I/Os" means that part of the I/O area is not used by I/O
modules but rather for the cyclic data exchange between SIMATIC
programmable controllers and passive stations on the bus. "Cyclic data
exchange" means that the CP 5430 TF sends the whole of the output area
assigned for ZP cyclically and updates the whole input area assigned for ZP
with the received data. You can use these virtual I/Os as proper inputs or
outputs. These addressed areas are processed normally with STEP 5
commands. The mode is cycle-synchronized or free. With the
CYCLE-SYNCHRONIZED mode, an HDB must be called at the checkpoints
B8976060/02 Communication with Cyclic I/Os
10 - 1 Volume 1