55
Precautions Section 2-2
If the Condition Flag is connected directly to the left bus bar, instruction B will
be executed based on the execution results of a previous rung if instruction A
is not executed.
Note Condition Flags are used by all instruction within a single program (task) but
they are cleared when the task switches. Therefore execution results in the
preceding task will not be reflected later tasks. Since conditions 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 is an exam-
ple.
Using Execution Results in N.C. and N.C. Inputs
The Condition Flags will pick up instruction B execution results as shown in
the example below even though the N.C. and N.O. 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.
Condition Flag
Example: =
Reflects instruction A execution
results.
Condition Flag
Example: =
Reflects instruction B execution
results.
Instruction B
Instruction A
Incorrect
Use
Condition Flag
Example: =
Reflects instruction A
execution results.
Instruction B
Instruction A
Reflects instruction A
execution results.
Condition Flag
Example: =
Correct
Use
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