1043
3. Instructions
CS/CJ/NSJ Series Instructions Reference Manual (W474)
Other Instructions
3
WDT
z Programming console settings
Note • The default value for the maximum cycle time is 1,000 ms, although it can be set anywhere from 1 to 40,000 ms in
10-ms units.
• WDT(094) can be used more than once in a cycle. When WDT(094) is executed more than once the cycle time
extensions are added together, although the total must not exceed 40,000 ms. If WDT(094) cannot be executed
again if the cycle has already been extended to 40,000 ms.
Related Auxiliary Area Words and Bits
Function
WDT(094) extends the maximum cycle time for the cycle in which this instruction is executed. The
watchdog timer setting in the PLC Setup is extended by an interval of T × 10 ms (0 to 39,990 ms).
When it is likely that the cycle time will increase due to a temporary increase in processing data, this
instruction can be used to prevent a cycle time error.
Example Programming
Operation of WDT(094)
The default maximum cycle time (1,000 ms) is used in this example.
• When CIO 0.00 turns ON, the first WDT(094) instruction extends the maximum cycle time by 300 ms
(30 × 10 ms). Thus, the maximum cycle time is 1,300 ms at this point.
• When CIO 0.01 turns ON, the second WDT(094) instruction attempts to extend the maximum cycle
time by another 39,000 ms. Since the new maximum cycle time (40,300 ms) exceeds the upper limit
of 40,000 ms, the extra 300 ms is ignored. As a result, the second WDT(094) instruction actually
extends the maximum cycle time by 38,700 ms.
• When CIO 0.02 turns ON, the third WDT(094) instruction attempts to extend the maximum cycle time
by another 1,000 ms. Since the maximum cycle time has already reached the upper limit of 40,000
ms, the third WDT(094) instruction is not executed.
Name Function Settings
Watch cycle time A Cycle Time Too Long error (fatal error) will be registered if the cycle
time exceeds the maximum setting.
0: Default setting (1,000 ms)
1: User time setting
Sets the maximum cycle time.
(This setting is valid only when the first setting has been set to 1.)
0001 to 0FA0
(1 to 40,000 ms, 10-ms units)
Name Address Operation
Cycle Time Too Long Flag A401.08 ON when the present cycle time exceeds the maximum cycle time (watch cycle time) set in
the PLC Setup. This is a fatal error which causes program execution to stop.
Maximum Cycle Time A262 and A263 These words contain the maximum cycle time in 32-bit binary. This value is updated every
cycle.
Present Cycle Time A264 and A265 These words contain the present cycle time in 32-bit binary. This value is updated every
cycle.
1
2
3
0.00
0.01
0.02
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