Siemens SIMATIC CPU 410 System Manual page 307

However, we offer you several specific blocks for optimizing your user program, e.g. in order
to improve its response to the extension of cycle times due to updates.
Specific blocks for S7–400H
In addition to the blocks supported both in the S7-400 and S7-400H systems, the S7-400H
software provides further blocks which you can use to influence the redundancy functions.
You can react to redundancy errors of the S7-400H using the following organization blocks:
● OB 70, I/O redundancy errors
● OB 72, CPU redundancy errors
SFC 90 "H_CTRL" can be used to influence fault-tolerant systems as follows:
● You can disable interfacing in the master CPU.
● You can disable updating in the master CPU.
● You can remove, resume or immediately start a test component of the cyclic self-test.
Note
Required OBs
Always download these error OBs to the S7-400H CPU: OB 70, OB 72, OB 80, OB 82,
OB 83, OB 85, OB 86, OB 87, OB 88, OB 121 and OB 122. If you do not download these
OBs, the fault-tolerant system goes into STOP when an error occurs.
Additional information
For detailed information on programming the blocks listed above, refer to the
with STEP 7
Functions
CPU 410 Process Automation/CPU 410 SMART
System Manual, 05/2017, A5E31622160-AC
System Software for S7-300/400; System and Standard
manual, and to the
Reference Manual.
Supplementary information
18.5 The STEP 7 user program
Programming
307