Maple Systems MAPware-7000 - Manual (Page 143)

135 MAPware-7000 Ladder Logic Guide
1010-1041 rev. 00
Instruction 88- Watchdog timer reset
Expression:
Space Requirement: 1 line x 3 column Location Requirement: Middle, Right rail
Function:
When the input is ON, this instruction extends the watchdog timer reset time. A watchdog
timer is a timer that runs in the background. If the timer reaches its preset timeout value, then
it forces a reinitialization of the HMC7000. This is a safety feature that forces the unit back to a
known state in case something unexpected happens. Therefore, under normal conditions, the
watchdog timer would never time out before it was reset by the HMC7000. However, you may
have an unusually long ladder logic program or a subroutine that causes the scan time to exceed
200 msec. This instruction can be used to extend the watchdog timeout by multiple of 1msec.
(i.e. if n = 1 => 201ms; if n = 100 => 300ms).
Execution Condition:
Input Operation Output
OFF No execution OFF
ON Execution ON
Operand:
Coil or Bit Register Constant Index
Name X Y B S T. C. M
X
W Y
W B
W S
W
T C D I J K
M
W
n Extend time 1-100
Example:
When B020 is ON, the scan time detection time is extended by 10 msec. (for a total of 210
msec).
Note
- The operand n specifies the extended time.
- The normal watchdog timeout is 200 ms