Principle Of Operation Of The Plcs; Functional Units - Siemens SIMATIC S5-90U System Manual

S5-90U/S5-95U
2.3

Principle of Operation of the PLCs

This section briefly describes the PLC's functional units processing your STEP 5 program.
2.3.1

Functional Units

S5-90U
S5-95U
ROM
Proces-
• Operating system
sor and
arith-
metic
unit
RAM
• STEP 5 program
• Timers
• Counters
• Flags
• PII/PIQ
Onboard I/Os
Programmer interface
Optional:
• SINEC L2 interface
• Second serial interface
E(E)PROM submodule
(can be plugged in)
S5-90U external I/O bus
S5-95U external I/O bus
EWA 4NEB 812 6115-02b
Figure 2-7. Functional Units of the PLCs
Technical Description
S5-100U
module(s)
IM 90
The IM 90 is
required for
the S5-90U
only.
The S5-95U
can be
expanded by
connecting
S5-100U
modules
directly.
2-7