AH500 Programming Manual 
6-232 
API 
Instruction code  Operand 
Function 
1004    DCNT   
S
1
, S
2
 
32-bit counter 
Device
X  Y  M  S  T  C  HC  D  L  SM  SR  E  PR  K  16#  “$”  DF 
Pulse instruction
16-bit instruction
32-bit instruction (5 steps)
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.