DVP-ES2/EX2/EC5/SS2/SA2/SX2/SE&TP Operation Manual - Programming
2.16 Applications of Special M Relays and D Registers
Contents:
These relays provide information of PLC operation in RUN status.
M1000:
NO contact for monitoring PLC status. M1000 remains “ON” when PLC is running.
M1000
Y0
PLC is running
Keeps being ON
Norm
ally ON contact
in PLC RUN status
M1001:
NC contact for monitoring PLC status. M1001 remains “OFF” when PLC is running.
M1002:
Enables single positive pulse for the first scan when PLC RUN is activated. Used to initialize
registers, ouptuts, or counters when RUN is executed..
M1003:
Enables single negative pulse for the first scan when PLC RUN is activated. Used to initialize
registers, ouptuts, or counters when RUN is executed.
PLC RUN
M1000
M1001
M1002
M1003
scan time
Contents:
1. Monitor timer is used for moitoring PLC scan time. When the scan time exceeds the set value
(SV) in the monitor timer, the red ERROR LED will be ON and all outputs will be “OFF”.
2. The default in the monitor timer is 200ms. If the program is long or the operation is too
complicated, MOV instruction can be used to modify SV. See the example below for SV =
300ms.
M1002
0
MOV K300 D1000
Initial pulse
3. The maximum SV in the monitor timer is 32,767ms. However, care should be taken when
adjusting SV. If SV in D1000 is too big, it cost much longer for operation errors to be detected.
Therefore, SV is suggested to be shorter than 200ms.
4. Scan time could be prolonged due to complicated instruction operations or too many I/O
modules being connected. Check D1010 ~ D1012 to see if the scan time exceeds the SV in
D1000. Besides modifying the SV in D1000, users can also apply WDT instruction (API 07).
When program execution progresses to WDT instruction, the internal monitor timer will be reset
and therefore the scan time will not exceed the set value in the monitor timer.
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