Edition 04/2002
英文版手册198页：

For a timer with a resolution of 1 ms, the timer bit and the current value are updated asynchronous to the
scan cycle. For scans greater than 1 ms, the timer bit and the current value are updated multiple times
throughout the scan.
For a timer with a resolution of 10 ms, the timer bit and the current value are updated at the beginning of
each scan cycle. The timer bit and current value remain constant throughout the scan, and the time
intervals that accumulate during the scan are added to the current value at the start of each scan.
For a timer with a resolution of 100 ms, the timer bit and current value are updated when the instruction is
executed; therefore, ensure that your program executes the instruction for a 100-ms timer only once per
scan cycle in order for the timer to maintain the correct timing.

也就是说，1ms定时是实时更新的，10ms定时Scan开始时更新一次，100ms定时是指令执行到时再更新。