Hold Operating State; Troubleshooting Operating State - Siemens SIMATIC S7-400H System Manual

8.4.5

HOLD operating state

Except for the additions described below, the behavior of the S7-400H CPU in HOLD
corresponds to that of a standard S7-400 CPU.
The HOLD state has an exceptional role, as it is used only for test purposes.
When is the HOLD operating state 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 if the fault-tolerant system remains in the redundant
8.4.6

TROUBLESHOOTING operating state

The TROUBLESHOOTING mode can only be adopted from the Redundant mode. During
troubleshooting, the CPUs exit the redundant mode, the other CPU becomes master and
continues to work in single mode.
Note
If the master CPU changes to STOP during troubleshooting, the troubleshooting is continued
on the standby CPU. However, when troubleshooting is completed, the standby CPU does not
start up again.
The self-test routine compares the master and standby CPUs, and reports an error if any
differences are found. Errors could be caused by hardware faults, checksum errors and
RAM/PIO comparison errors.
The following events will trigger the TROUBLESHOOTING state:
1. If a one-sided call of OB 121 (on only one CPU) occurs in redundant mode, the CPU
2. When a checksum error occurs on only one of the redundant CPUs, that CPU enters the
3. When a RAM/PIO comparison error is detected in redundant mode, the standby CPU
S7-400H
System Manual, 09/2007, A5E00267695-03
the standby CPU remains in STOP and outputs a diagnostics message.
state.
assumes a hardware fault and enters the TROUBLESHOOTING state. The partner CPU
assumes master mode as required, and continues operation in single mode.
TROUBLESHOOTING state. The partner CPU assumes master mode as required, and
continues operation in single mode.
enters the TROUBLESHOOTING state (default reaction), and the master CPU continues
operation in single mode.
The reaction to RAM/PIO comparison errors can be modified in the configuration (for
example, the standby CPU goes into STOP).
System and operating states of the S7-400H
8.4 The operating states of the CPUs
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