14.5 Instruction of Leading Edge Detection Method14.5.1 Instructions of Leading Edge Detection MethodInstructions using the leading edge detection operation1. DF (leading edge differential) instructions2. Count input for CT (counter) instructions3. Count input for F118 (UDC up-down counter) instructions4. Shift input for SR (shift register) instructions5. Shift input for F119 (LRSR left-right shift register) instructions6. NSTP (next step) instructions7. Differential execution type high-level instruction (P13)Leading edge detection method• An instruction with a leading edge detection method operates only in the scan where its trigger(execution condition) is detected switching from off to on.(1) Standard operation(2) Leading edge detection operationHow to perform leading edge detectionThe condition of the previous execution and the condition of the current execution are compared, and theinstruction is executed only if the previous condition was off and the current condition is on. In any othercase, the instruction is not executed.Precautions when using an instruction which performs leading edge detection• When RUN begins, for example when the system is powered on, the off→ on change of the executioncondition (trigger) is not detected. The instruction is not executed. Execution of the instruction will takeplace as explained on the next page.• When used with one of the instructions indicated in instructions 1 to 6 below which change the order ofexecution of instructions, the operation of the instruction may change depending on input timing. Takecare regarding this point.Be careful when using leading edge detection type instructions with control instructions, suchas:1. MC and MCE instructions2. JP and LBL instructions3. LOOP and LBL instructions4. CNDE instruction5. Step ladder instructions6. Subroutine instructionsPhone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: info@clrwtr.com
