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OB 21
MANUAL WARM RESTART
MANUAL RETENTIVE COLD
RESTART
CPU 948 Programming Guide
C79000-G8576-C848-04
If the CPU performs a MANUAL COLD RESTART or RETENTIVE
MANUAL COLD RESTART, the system program calls OB 21 once.
Here, you can store a STEP 5 program which executes preliminary
steps for a warm restart of the cyclic program.
With a MANUAL WARM RESTART, the cyclic program is
continued with the next statement following the point at which it was
interrupted after processing OB 21, the sequence is as follows:
• • The BASP signal (disable command output) remains active during
the processing of the remaining cycle and is only switched inactive
at the beginning of the next (complete) cycle.
• • The process image of the outputs is reset at the end of the
remaining cycle.
• • If OB 21 is not loaded, the CPU begins again at the point at which
the program was interrupted on completion of the MANUAL
WARM RESTART and the system activities.
If the parameter "COLD RESTART WITH MEMORY" is entered in
the data block DX 0, after processing OB 21, 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.
START-UP Mode
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