Table 10-8 Example Of Redundant I/O, Ob 1 Part - Siemens SIMATIC S7-400H System Manual

Using I/Os in S7-400H
10.6 Other options for connecting redundant I/Os
Example in STL
The required elements of the user program (OB 1, OB 122) are listed below.
Table 10-8 Example of redundant I/O, OB 1 part
STL
NOP 0;
SET;
R ATTEMPT2;
A MODA;
JCN CMOB;
CMOA: SET;
R IOAE_BIT;
L PID 8;
A IOAE_BIT;
JCN IOOK;
A ATTEMPT2;
JC CMO0;
SET;
R MODA;
S ATTEMPT2;
CMOB: SET;
R IOAE_BIT;
L PID 12;
A IOAE_BIT;
JCN IOOK;
A ATTEMPT2;
JC CMO0;
SET;
S MODA;
S ATTEMPT2;
JU CMOA;
CMO0: L SUBS;
IOOK:
154
Description
//Initialization
//Read module A first?
//If not, continue with module B
//Delete IOAE bit
//Read from CPU 0
//Was IOAE detected in OB 122?
//If not, process access OK
//Was this access the second attempt?
//If yes, use substitute value
//Do not read module A first any more
//in future
//Delete IOAE bit
//Read from CPU 1
//Was IOAE detected in OB 122?
//If not, process access OK
//Was this access the second attempt?
//If yes, use substitute value
//Read module A first again in future
//Substitute value
//The value to be used is in ACCU1
System Manual, 09/2007, A5E00267695-03
S7-400H