Technical data

4.4.5

Interruptions in the

RESTART Mode

A start-up program can be interrupted by the following:

•• NAU (power failure) or PEU (power failure in expansion unit),

•• activating the stop switch, the stop operation, MP-STP or PG-STP,

•• program and device errors (see Section 5.6).

If you want to continue an interrupted RESTART with one of the

possible restart types, please remember the following points:

Power failure at RESTART

After power returns following a power failure you must distinguish

between the situations listed in the following table:

Selected mode: AUTOMATIC WARM RESTART

The CPU is performing a COLD RESTART (OB 20):

following the return of power after power failure, the organization block OB 22 (AUTOMATIC

WARM RESTART) is activated at the point of interruption in OB 20.

The CPU is performing a MANUAL WARM RESTART (OB 21):

following the return of power after a power failure, organization block OB 22 (AUTOMATIC WARM

RESTART) is activated at the point of interruption in OB 21.

The CPU is already performing an AUTOMATIC WARM RESTART (OB 22):

following the return of power after a power failure, no second OB 22 is activated. The interrupted

OB 22 is not continued after the return of power but is aborted and then called again and processed

from the beginning.

AUTOMATIC COLD RESTART

The CPU is performing a MANUAL or AUTOMATIC COLD RESTART or a MANUAL WARM

RESTART:

following the return of power after power failure, the interrupted OB 20 or OB 21 is not continued, but

abandoned and the newly called OB 20 is processed.

The same rules apply to an AUTOMATIC WARM RESTART

following a PEU signal.

RESTART Mode

CPU 928B Programming Guide

C79000-B8576-C898-01

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