Power failure/return of power
When power is shut off and then restored, the coordinator starts
automatically. In this case, all CPUs execute an AUTOMATIC
WARM RESTART or an AUTOMATIC COLD RESTART,
depending on the setting in DX 0 (see Chapter 7).
The start-up of the individual CPUs in multiprocessor operation is
synchronized. Each CPU waits until all others have ended their
initialization phase. Then they begin their cycle simultaneously.
However, you can use a setting in DX 0 to cancel start-up
synchronization.
10.1.8
Test Mode Proceed as follows:
1. Make sure that the "test mode" function is enabled on the
coordinator.
2. Switch the mode selector on the COR from STOP to TEST.
The BASP LED goes off.
3. Go through a COLD RESTART or WARM RESTART on the
CPUs you want to change to the RUN mode.
Special features of test
operation
In test operation, you can run CPUs individually or in any combination.
CPUs in the STOP mode cannot disable the entire PLC.
Start-up of individual CPUs is not synchronized in test operation. The
CPUs begin their cyclic operation at different times according to the
length of the start-up organization blocks OB 20, OB 21 or OB 22.
If an error occurs in one CPU during test operation, only that CPU goes
into the STOP mode. The error does not affect the other CPUs.
Warning
Since no CPU can output the BASP signal in case of an error
in the test mode, the test mode must be switched inactive after
successful installation to avoid a critical or even dangerous
situation arising in the system.
Multiprocessor Mode
CPU 948 Programming Guide
10 - 14 C79000-G8576-C848-04
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