The User Program - Siemens SIMATIC S7-400H System Manual

S7-400H installation options

3.7 The user program

3.7 The user program
The rules of designing and programming a standard S7-400 system also apply to the S7-400H.
In terms of user program execution, the S7-400H behaves in exactly the same manner as a
standard system. The integral synchronization functions of the operating system are executed
automatically in the background. You do not need to configure these functions in your user
program.
In redundant operation, the user programs are stored identically and executed synchronously
and event-driven on both CPUs.
However, we offer you various blocks which you can use to tune your program in order to
improve its response to any extension of cycle times due to operations such as updates.
Specific blocks for S7-400H
In addition to the blocks supported in the S7-400 and S7-400H systems, the S7-400H software
provides further blocks 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 link-up 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.
Further information
For detailed information on programming the blocks listed above, refer to the
with STEP 7
Functions
32
NOTICE
Required OBs
Always download the following 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 ignore this,
the fault-tolerant system changes to STOP when an error occurs.
manual, and to the
reference manual.
System Software for S7-300/400; System and Standard
Programming
System Manual, 09/2007, A5E00267695-03
S7-400H