Determining The Primary Cpu With "Rh_Getprimaryid - Siemens SIMATIC S7-1500 System Manual

Basics of program execution
10.4 Special instructions for S7-1500R/H redundant systems
10.4.2

Determining the primary CPU with "RH_GetPrimaryID"

You use the "RH_GetPrimaryID" instruction to read out which CPU is currently the primary
CPU. The instruction outputs the redundancy ID of the primary CPU at the Ret_Val block
parameter.
Figure 10-4
Example: Reading maintenance information from the SIMATIC memory card of the primary CPU
Proceed as follows to read specific maintenance information from the SIMATIC memory card
of the primary CPU:
1. Get the redundancy ID of the primary CPU with "RH_GetPrimaryID".
2. Read the maintenance information from the SIMATIC memory card of the primary CPU with
"GetSMCInfo".
– If the CPU with redundancy ID 1 is the primary CPU, enter "12" at the Mode block
– If the CPU with redundancy ID 2 is the primary CPU, enter "22" at the Mode block
Reference
You can find more information on the "RH_GetPrimaryID" instruction in the STEP 7 online
help.
332
"RH_GetPrimaryID" instruction
parameter ("1" for redundancy ID, "2" for maintenance information).
parameter ("2" for redundancy ID, "2" for maintenance information).
S7-1500R/H redundant system
System Manual, 01/2024, A5E41814787-AF