Technical data

3 Fundamentals of the Model
To understand the procedure and to be able to work with the system, the
user must be familiar with the model and the terminology. This chapter first
explains the architecture, then the communications model and its
terminology and finally the simulation on programmable controllers.
To keep the explanation of terminology clear, some general terms are
explained in the appendix.
The basic aims of the communication described in this volume are as
follows:
➣ Simple data exchange via layer 2 (ISO/OSI),
➣ Limited volume of transmitted and received data to improve
performance,
➣ Simple handling.
This model includes two basic types of communication:
➣ Implicit communication is handled in the SIMATIC PLC by means of I/O
bytes, consisting of the distributed I/Os (DP) cyclic I/Os (ZP) and global
I/Os (GP). Implicit communication is controlled by the communications
processor (CP).
The
exceptions
in this case are the cycle-synchronized communication
modes of the DP, ZP and GP. Here, handling blocks are used for
synchronization.
The cyclic I/Os (ZP) mode is only possible with the CP 5430 TF.
➣ Explicit communication is handled in the SIMATIC PLC by the handling
blocks within the system, consisting of S5-S5, FMA and free layer 2
communication.
B8976060/02 Fundamentals of the Model
3 - 1 Volume 1