Chapter 6 Applied Instructions API 1004 Symbol: S 1 ： Counter value Double word S 2 ： Setting value of the counter Double word Explanation: 1. The instruction DCNT can be used to enable the 32-bit counter within the range between HC0 and HC63. 2. When the instruction DCNT is executed, the switch between the 32-bit general-purpose addition counters and the 32-bit general-purpose subtraction counters depends on states of the special auxiliary relays SM621~SM684. 3. When the instruction DCNT is not executed, the counter stops counting, and the original value of the counter is not cleared. Users can use the instruction RST to clear the value of the counter and reset the contact. Example:
When the PLC runs, SM621 is OFF, and the value of HC0 is cleared. When SM408 is ON for the first time, the setting value 10 is loaded to HC0, and HC0 begins to count up. After SM408 is switched from OFF to ON ten times, the value of HC0 is 10, and the contact of HC0 is ON. After HC0 is ON, the value of HC0 keeps increasing because SM408 is still switched from OFF to ON. When the value of HC0 is 20, SM621 is ON. After SM408 is switched from OFF to ON ten times, the contact of HC0 is OFF. After the contact of HC0 is OFF, the value of HC0 keeps decreasing because SM408 is still switched from OFF to ON.
6-233 Instruction code Operand Function DCNT S , S 1 2 32-bit counter Device X Y M S T C HC D L SM SR E PR K 16# “$” DF S 1 S 2 Pulse instruction 16-bit instruction 32-bit instruction (5 steps) － AH500