Technical data

4.3 STOP Mode
4.3.1
Characteristics and
Indication of the Operating
Mode
The STOP mode is distinguished by the following features:
User program The user program is not processed.
Retention of data If program execution has already been active, the values of counters,
timers, flags and process images are retained at the transition to the
stop mode.
BASP signal The BASP signal (disable command output) is active. This disables all
digital outputs.
Exception: In multiprocessor mode the BASP signal is not active
during the test mode of the coordinator - please see your System
Manual (/2/ in Chapter 13) for more information.
ISTACK If program execution was already active, there is an information field
for each interrupted program processing level in the interrupt stack
(ISTACK) that indicates the cause of the interrupt when the CPU is in
the STOP mode (see Section 5.4).
LEDs on the front panel
of the CPU
RUN LED: off
STOP LED: on (steady or flashing)
BASP LED: on (except in test mode)
The STOP LED indicates the possible causes of the current stop state.
The following paragraphs describe a continuously lit or flashing
STOP LED.
4
STOP Mode
CPU 928B Programming Guide
C79000-B8576-C898-01
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