Data Exchange Between Higher- And Lower-Level Io System - Siemens S7-1200 System Manual

Unit 1 and unit 2 each consist of an I-device with centralized I/O. The I-device along with the
distributed I/O system (for example, ET 200) forms unit 3.
The user program on the I-device is responsible for preprocessing the process data. For this
task, the user program of the I-device requires default settings (for example, control data)
from the higher-level IO controller. The I-device provides the higher-level IO controller with
the results (for example, status of its subtask).
10.2.7.4

Data exchange between higher- and lower-level IO system

Transfer areas are an interface to the user program of the I-device CPU. Inputs are
processed in the user program and outputs are the result of the processing in the user
program.
The data for communication between IO controller and I-device is made available in the
transfer areas. A transfer area contains an information unit that is exchanged consistently
between IO controller and I-device. You can find more information on configuration and use
of transfer areas in the section "Configuring the I-device".
The next figure shows the data exchange between the higher- and lower-level IO system.
The individual communication relations are explained below based upon the numbers:
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
Communication
10.2 PROFINET
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