Scan Time Restriction - Mitsubishi Electric MELSEC-KOJIU Instruction Manual

5 . EXPLANATION OF PROGRAM
5.4.17 Scan time restriction
The check time of arithmetic operation watchdog timer (WDT) of KOJ1 U is 0.1 second.
The CPU resets the WDT after END instruction. When scan time exceeds 0.1 second, WDT
error occurs and all outputs are turned off by hardware.
I
peripheral unit intervention time (T2)
I
Scan time (Ts) = instruction execution time (TI
+
(Max. 10mS)
Example of maximum instruction execution time
Max. instruction execution time = 1OOms
-
1 Oms = 90mS
(T2)
II
0
Instruction execution time measuring method
Output
indicator
LED
1. Add the following program to the prepared program.
Unused M
Dd: Unused data register
D d + l + D d
Dd
-*
Y20
-
27
2.
When the sequencer is run, Y20 to Y27 displays are in-
dicated with 0
-
255
-
0. Therefore, measure the time
T, i.e. from when Y20 to Y27 are all turned off to
when they are all turned on again.
3 . Overall instruction execution time (T1 )
I T 1 = T/2561
85