Siemens Simatic S7-1500R System Manual page 259

Maintenance
11.1 Replacing components of the S7-1500R/H redundant system
Checking pairing state
You have the following options for checking the pairing state:
● Directly from the display of the backup CPU.
In the "Overview > Redundancy > Pairing state" menu:
– Paired
– Single paired (X*P*)
– Not paired
– Not paired - Too many partners
– Not paired - Article ID mismatch
– Not paired - Firmware mismatch
Example: Paired
258
Primary CPU Backup CPU
S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA