Using I/Os in S7–400H
13.5 Other options for connecting redundant I/Os
S7-400H
System Manual, 03/2012, A5E00267695-11
209
The sample program is based on the fact that following an access error on module A and its
replacement, module B is always processed first in OB 1. Module A is not processed first
again in OB 1 until an access error occurs on module B.
NOTICE
The MODA and IOAE_BIT variables must also be valid outside OB 1 and OB 122. The
ATTEMPT2 variable, however, is used only in OB 1.
5HWU\ )DOVH
5HDGPRGXOH
$ILUVW"
<HV
1R
<HV
<HV
<HV
<HV
1R
1R
1R
1R
$FFHVVWR
PRGXOH$
,2DFFHVV
HUURU"
$FFHVVWR
PRGXOH%
,2DFFHVV
HUURU"
b
'RQRWUHDG
PRGXOH$ILUVWDQ\
PRUHLQIXWXUH
5HWU\ 758(
b
'RQRWUHDG
PRGXOH%ILUVWDQ\
PRUHLQIXWXUH
5HWU\ 758(
5HWU\
758("
5HWU\
758("
8VHVXEVWLWXWH
YDOXH
8VHYDOXHRI
PRGXOH$
8VHYDOXHRI
PRGXOH%
Figure 13-14 Flow chart for OB 1