Flowchart For Ob1 - Siemens SIMATIC S7-400H Manual

Using I/O on the S7-400H
Yes
Access to
Read module A
I/O
access
error?
2nd attempt
== TRUE?
No
Use value of
Read module A
Use
Figure 7-14

Flowchart for OB1

7-38
2nd attempt: = WRONG
Read module A
first?
Read mod. A first
any more in
future
2nd attempt: = TRUE
Yes
No
Yes
use
substitute
value
No
Read mod. A first
again in
future
2nd attempt: = TRUE
Yes
No
2nd attempt
== TRUE?
Yes
Automation System S7-400H Fault-tolerant Systems
Access to
module B
I/O
access
error?
No
Use value of
module B
Use
A5E00068197-07