Technical data

4.1 Introduction and Overview
The CPU 928B has three operating modes:
•• STOP mode
•• RESTART mode
•• RUN mode
In the RESTART and RUN modes, certain events can occur to which
the system program has to react. In many cases, a specific
organization block (a block from OB 1 to OB 35) is called as a
reaction to an event and serves as the user interface.
The modes are displayed by LEDs on the front panel of the CPU.
Some of the modes must be activated using the operating elements on
the front panel of the CPU. The position of the LEDs and operating
elements can be seen in Fig. 4-1.
SIEMENS
6ES5 948-3UA11
RUN
STOP
RUN
STOP
SYS FAULT
RESET
RÜCKSETZEN
URLÖSCHEN
OVERALL
RESET
QVZ
ADF
ZYK
BASP
INIT
SI1
SI2
Receptacle for
S5-155U CPU948
memory card
Mode selector
LED (green)
LED (red)
LED (red)
Reset switch
Error display LEDs (red)
Error display LED (red)
Interface error LEDs (red)
Order number and version
Interface SI1
PG interface, 15-pin
Lever
Securing bolt
SI1
SI2
Second serial interface SI2
Receptacle for interface submodule
Fig. 4-1 Front panel of the CPU 928B with display and operating elements
Introduction and Overview
CPU 928B Programming Guide
4 - 4 C79000-B8576-C898-01