Siemens SIMATIC S7-400H System Manual page 454

Differences between fault-tolerant systems and standard systems
Function
Information in the system status
list
Update monitoring
SSL ID W#16#0232 index
W#16#0004 byte 0 of the "index"
word in the data record
454
Additional programming
You can also obtain data records for the fault tolerance-

specific LEDs from the partial list with SSL ID W#16#0019.
You can also obtain data records for the redundancy error OBs

from the partial list with SSL ID W#16#0222.
You can obtain information on the current status of the fault-

tolerant system from the partial list with SSL ID W#16#xy71.
You can also obtain data records for the fault tolerance-

specific LEDs from the partial list with SSL ID W#16#0174.
The partial list with the SSL ID W#16#xy75 provides

information on the status of the communication between the
fault-tolerant system and switched DP slaves.
The operating system monitors the following four configurable
timers:
Maximum cycle time extension

Maximum communication delay

Maximum inhibit time for priority classes > 15

Minimum I/O retention time

No additional programming is required for this. For more detailed
information, refer to chapter Link-up and update (Page 141).
Fault-tolerant CPU in stand-alone mode: W#16#F8
Fault-tolerant CPU in single mode: W#16#F8 or W#16#F9
Fault-tolerant CPU in redundant mode: W#16#F8 and W#16#F1
or W#16#F9 and W#16#F0
System Manual, 03/2012, A5E00267695-11
S7-400H