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START-UP Mode
OB 22
AUTOMATIC WARM
RESTART
AUTOMATIC RETENTIVE
COLD RESTART
4 - 26
When the CPU executes an AUTOMATIC WARM RESTART or
AUTOMATIC RETENTIVE COLD RESTART, the system program
calls OB 22 once. Here, you can store a STEP 5 program which
executes preliminary steps (generally following a power failure) for a
warm restart of cyclic program execution.
Following POWER UP, the CPU executes the system activities listed
in Section 4.4.4 for a warm restart and attempts to resume the program
at the point at which it was interrupted.
OB 22 is called first.
After executing OB 22, the interrupted program execution is resumed
with the next statement following the point at which the program was
interrupted.
Following a power failure and the return of power:
• • The BASP signal (disable command output) remains active during
the remaining cycle and is only switched inactive at the beginning
of the first complete cycle.
• • The process image of the outputs is reset at the end of the
remaining cycle.
• • If OB 22 is not loaded, the CPU resumes program processing
immediately at the point of interruption at the end of the
AUTOMATIC WARM RESTART.
If the parameter "COLD RESTART WITH MEMORY" is entered in
the data block DX 0, after processing OB 22, the system program then
goes through a COLD RESTART (the CPU resumes program
execution with the first STEP 5 statement in OB 1). The signal
states of the flags, IPC flags, semaphore and the block address list
(DB 0) are retained.
CPU 948 Programming Guide
C79000-G8576-C848-04
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