Hold Mode; Error-Search Mode - Siemens SIMATIC S7-400H System Manual

11.3.5

HOLD mode

Except for the additions described below, the behavior of the S7-400H CPU in HOLD mode
corresponds to that of a standard S7-400 CPU.
The HOLD mode has an exceptional role, as it is used only for test purposes.
When is the HOLD mode possible?
A transition to HOLD is only available during STARTUP and in RUN in single mode.
Properties
● Link-up and update operations are not available while the fault-tolerant CPU is in HOLD
● It is not possible to set breakpoints when the fault-tolerant system is in redundant system
11.3.6

ERROR-SEARCH mode

The ERROR-SEARCH mode can only be adopted from the redundant system mode. During
troubleshooting, the redundant system mode is exited, the other CPU can become master
and continue to work in standalone mode.
Note
If the master CPU changes to STOP during troubleshooting, the troubleshooting is continued
on the standby CPU. However, once troubleshooting is completed, the standby CPU does
not start up again.
The following events will trigger ERROR-SEARCH mode:
1. If a one-sided call of OB 121 (on only one CPU) occurs in redundant mode, the CPU
2. If a checksum error occurs on only one CPU in redundant mode, that CPU enters
3. If a RAM/POI comparison error is detected in redundant mode, the standby CPU enters
S7-400H
System Manual, 03/2012, A5E00267695-11
mode; the reserve CPU remains in STOP and outputs a diagnostics message.
mode.
assumes a hardware fault and enters ERROR-SEARCH mode. The partner CPU
assumes master mode as required, and continues operation in standalone mode.
ERROR-SEARCH mode. The partner CPU assumes master mode as required, and
continues operation in standalone mode.
ERROR-SEARCH mode (default response), and the master CPU continues operation in
standalone mode.
The response to RAM/POI comparison errors can be modified in the configuration (for
example, the standby CPU goes into STOP).
System and operating states of the S7–400H
11.3 The operating states of the CPUs
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