Hold Operating Mode - Siemens SIMATIC S7-400H Manual

System and Operating Modes of the S7-400H
4.3.5

HOLD Operating Mode

With the exception of the additions described below, the S7-400H in HOLD mode
behaves in exactly the same way as a regular CPU on the S7-400.
The HOLD mode is a special case. It is only used for test purposes.
When is the HOLD mode possible?
The HOLD mode can be reached only from the STARTUP mode and from RUN
submode of Solo mode.
Properties
While the CPU 417-4H is in the HOLD mode, link-up and update are not
possible; the standby CPU remains at STOP and a diagnostic message is
issued.
If the S7-400H is in the Redundant system mode, breakpoints cannot be set.
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S7-400H Programmable Controller Fault-Tolerant Systems
A5E00068197-04