Usage Of 1Ms Timer - Mitsubishi Electric MELCEC Q Series User Manual

4. CPU MODULE
4.4.2

Usage of 1ms timer

(1)
(2)
(3)
With QCPU-A, a 1ms timer can be used in addition to the conventional high-speed
timer (10ms) and low-speed timer (100ms).
Usage
Adding ZHTIME, a 1ms timer setting instruction, in a program enables the use of a
1ms timer. (The ZHTIME instruction must be written in the main program.)
The ZHTIME instruction is checked at start-up and at switching from STOP to RUN.
When this instruction exists in the main program, the 1ms timer can be used.
If the ZHTIME instruction does not exist in the main program, only the 100ms/10ms
timer can be used, and the 1ms timer is disabled.
The number of occupied points is set as the total points of the 100ms timer, 10ms
timer, retentive timer, and 1ms timer.
The area for the 1ms timer is reserved following that of the retentive timer.
Consequently, the constant specified with the ZHTIME instruction is designated as
the device number following that of the retentive timer specified by parameters in the
unit of 16 points.
Use example of the ZHTIME instruction
The following shows the use example of the ZHTIME instruction.
Example) When the timer in 1ms is set at T208 or later:
M9037
Accuracy of 1ms timer
The following table shows the accuracy of 1ms timer.
Timer Type
1ms
LEDB ZHTIME
SUB K208
LEDR
Scan Time
T 1ms
T 1ms
4 - 36
Designate the
device
in the unit of 16
points.
Accuracy
+2 scan time to -1ms
+2 scan time to -1 scan time