Omron FQM1-MMA21, FQM1-CM001 Programming Precautions, Appendix A, Using Condition Flags

Programming Appendix A

Programming Precautions

Condition Flags

Using Condition Flags

Condition flags are shared by all instructions, and will change during a cycle depending on results of executing individual instructions. Therefore, be sure to use Condition Flags on a branched output with the same input condition immediately after an instruction to reflect the results of instruction execution. Never connect a Condi- tion Flag directly to the bus bar because this will cause it to reflect execution results for other instructions.

Example: Using Instruction A Execution Results

Correct Use

a

	Instruction A
	Reflects instruction A
Condition Flag	execution results.
Example: =
	Instruction B

Mnemonic

Instruction	Operand
LD	a
Instruction A
AND	=
Instruction B

The same input condition (a) is used for instructions A and B to execute instruction B based on the execution results of instruction A. In this case, instruction B will be executed according to the Condition Flag only when instruction A is executed.

Incorrect Use
	Preceding rung
	Instruction A
	Reflects the execution results of
	the preceding rung if instruction
Condition Flag	A is not executed.
Example: =
	Instruction B

If the Condition Flag is connected directly to the left bus bar, instruction B will be executed based on the execu- tion 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.

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