When the execution result is 0, the system variable #L_CalcZero turns ON.
When checking the result using system variables, make sure the check takes place after the instruction has been executed. When checking the state after multiple instructions have been executed, system variables will store the result only of the last processed instruction.
Program Example
XOR
When the positive transition instruction turns ON, the XOR instruction will be executed. When the XOR instruction is executed, the result value obtained by XORing Data_A with FOFF is stored in D1.
When using a normally open instruction, as long as the instruction variable is ON, the XOR instruction is always executed.
XORP
When the normally open instruction turns ON, the XORP instruction will be executed. When the XORP instruction is executed, the result value obtained by XORing Data_A with FOFF is stored in D1.
Even when using a normally open instruction, the XORP instruction executes only when it detects the upward transition.
Even if the normally open instruction variable remains ON,, the XORP instruction is executed only for one scan.