The Programmable Controllers' Principle Of Operation; Functional Units - Siemens SIMATIC S5-95F Manual

S5-95F
2.4

The Programmable Controllers' Principle of Operation

This section describes how the controller processes your program.
2.4.1

Functional Units

Basic unit
CPU
PII
Timers
Counters
Flags
PIQ
Onboard
inputs
(digital,
interrupt,
counter)
Onboard I/Os
Figure 2-3. Functional Units of a Basic Programmable Controller
EWA 4NEB 812 6210-02
Operating
system
Arithmetic
(ROM)
unit
Processor
Onboard
outputs
(digital)
Design, Functions and Operation
Control
program
and data
blocks
(RAM)
External
I/O bus
Input
modules
(digital,
analog)
Functional
modules
Failsafe and non-failsafe modules
Memory
submodule
(EPROM)
Serial
interface
Redundant
link via
fiber optic
cable
Output
modules
(digital,
analog)
2-5