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Programming Appendix A
Since condition flags are shared by all instructions, make absolutely sure that they do not interfere with each
other within a single ladder-diagram program. The following are examples.
1. Using Execution Results in NC and NO Inputs
The Condition Flags will pick up instruction B execution results as shown in the example below even though
the NC and NO input bits are executed from the same output branch.
Make sure each of the results is picked up once by an OUTPUT instruction to ensure that execution results
for instruction B will be not be picked up.
Incorrect
Use
Condition Flag
Example: =
Condition Flag
Example: =
Reflects instruction B
execution results.
Reflects instruction A
execution results.
Instruction B
Instruction A
C
D
C
D
Correct
Use
Instruction A
Instruction B
Reflects instruction A
execution results.
Condition Flag
Example: =
Condition Flag
Example: =
Reflects instruction A
execution results.