Siemens CPU 948, Programming Manual

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4.3.8
Interruptions during
START-UP
A start-up program can be interrupted by the following:
••
power failure in the central controller (NAU) or in the expansion
unit (PEU),
••
stop switch, stop command, HALT or PG-STPor
••
program errors or device faults (refer to Section 5.5).
Basic rules for an interrupted
START-UP
The following basic rules apply to the start-up response of the
CPU 948:
If the START-UP is interrupted, the subsequent START-UP is
always restarted from the beginning.
The last selected type of start-up is selected. Example:
1. POWER DOWN (NAU) in the cycle
2. Switch set to STOP
3. POWER UP
4. Switch set to RUN
Reaction: the CPU executes a MANUAL WARM RESTART
An interrupted COLD RESTART cannot be continued with a
WARM RESTART, but must be repeated.
Following an interrupted WARM RESTART, both a COLD
RESTART and a new WARM RESTART are possible.
Response of the CPU on the
return of power after power
failure or PEU signal
If the start-up execution is interrupted by a power failure or the PEU
signal, the response of the CPU when power returns depends on the
set and interrupted mode. The following table provides an overview.
Mode set in DX 0 Interrupted mode Interrupted
start-up OB
Reaction of the CPU
AUTOMATIC
COLD RESTART MANUAL
COLD RESTART OB 20 Depending on the prior events, an
AUTOMATIC COLD RESTART is
executed (OB 20 is called and
processed from the beginning).
No "remaining start-up" is
processed, (OB 20 or OB 21 is not
resumed).
MANUAL
WARM RESTART OB 21
AUTOMATIC
COLD RESTART OB 20
AUTOMATIC
WARM RESTART MANUAL
COLD RESTART OB 20 STOP
MANUAL
WARM RESTART OB 21 An AUTOMATIC WARM RESTART
is executed (OB 22 is called and
processed from the beginning);
no "remaining start-up" is processed
(OB 21 or OB 22 is not resumed).
AUTOMATIC
WARM RESTART OB 22
START-UP Mode
CPU 948 Programming Guide
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C79000-G8576-C848-04