Справочник Пользователя для Mitsubishi Electronics FX3G
865
FX
3S
/FX
3G
/FX
3GC
/FX
3U
/FX
3UC
Series
Programming Manual - Basic & Applied Instruction Edition
37 Operation of Special Devices (M8000 -, D8000 -)
37.2 Supplement of Special Devices (M8000 - and D8000 -)
31
FNC277
-F
NC2
79
79
Da
ta
Trans
fer 3
fer 3
32
FNC28
0-F
NC
289
289
H
igh-Speed
Process
ing 2
33
FNC2
90-
FNC299
FNC299
Ex
tensi
on Fi
le
le
Register C
ontrol
34
FN
C300-
FNC30
5
FX
3U
-C
F-
AD
P
35
SFC
•STL
Programming
36
Interrupt
Function
37
Sp
ec
ia
l D
evi
ce
38
E
rror Code
A
Ve
rsi
on U
p
Inform
ati
on
B
Ex
ecuti
on
T
imes
37.2.2 Watchdog timer [D8000]
The watchdog timer monitors the operation (scan) time of the PLC. When the operation is not completed within the
specified time, ERROR (ERR) LED light turns on and all outputs are turned OFF.
When the power is initially turned ON, "200 ms" is transferred from the system to D8000 as the default value. For
executing a program beyond 200 ms, the contents of D8000 must be changed by the user program.
specified time, ERROR (ERR) LED light turns on and all outputs are turned OFF.
When the power is initially turned ON, "200 ms" is transferred from the system to D8000 as the default value. For
executing a program beyond 200 ms, the contents of D8000 must be changed by the user program.
1. Example program
2. When a watchdog timer error occurs
A watchdog timer error may occur in the following cases. Add the above program to somewhere near the first step or
adjust the number of execution FROM/TO instructions at the same scan.
1) When using many special function units/blocks
adjust the number of execution FROM/TO instructions at the same scan.
1) When using many special function units/blocks
When many special function units/blocks (such as positioning, cam switches, link and analog) are used, buffer
memory initial setting time becomes long at turning on the PLC, thus extending the operation time and allowing
the possibility for a watchdog timer error to occur.
memory initial setting time becomes long at turning on the PLC, thus extending the operation time and allowing
the possibility for a watchdog timer error to occur.
2) When executing many FROM/TO instructions at the same time
When many FROM/TO instructions are executed or when many buffer memories are transferred, it extends the
scan time, and a watchdog timer error may occur.
scan time, and a watchdog timer error may occur.
3) When using many high-speed counters (software counters)
When many high-speed counters are programmed and high frequency is counted at the same time, it extends the
scan time, and a watchdog timer error may occur.
scan time, and a watchdog timer error may occur.
3. How to reset the watchdog timer
The watchdog timer can be reset in the middle of a sequence program using WDT (FNC 07) instruction.
It is recommended to reset the watchdog timer by WDT (FNC 07) instruction when the scan time of a particular
sequence program is extended or when many special function units/blocks are connected.
It is recommended to reset the watchdog timer by WDT (FNC 07) instruction when the scan time of a particular
sequence program is extended or when many special function units/blocks are connected.
→ For WDT (FNC 07) instruction, refer to Section 8.8.
4. Cautions on changing the watchdog timer
The watchdog timer time can be set to a maximum of 32767 ms. However, CPU error detection is delayed when the
watchdog timer time is extended.
It is recommended to use the default value (200 ms) when no problems are to be expected in operation.
The watchdog timer time becomes "0" when a value less than "0" is set to D8000.
watchdog timer time is extended.
It is recommended to use the default value (200 ms) when no problems are to be expected in operation.
The watchdog timer time becomes "0" when a value less than "0" is set to D8000.
37.2.3 Battery voltage low detection [M8005 and M8006]
This special device detects low voltage in the lithium battery for memory backup.
In FX
In FX
3U
/FX
3UC
PLCs, the BATT (BAT) LED turns ON when the PLC detects low battery voltage.
In FX
3G
/FX
3GC
PLCs, the ALM LED indicator turns ON when the PLC detects low battery voltage if the optional battery
is installed and the battery mode is selected by the parameter setting.
Use the following program to notify low battery voltage to the outside.
Use the following program to notify low battery voltage to the outside.
M8002
Initial pulse
FNC 12
MOV
K300
D8000
FNC 07
WDT
Setting value of watchdog timer is set to "300 ms".
0
The watchdog timer
When WDT (FNC 07) instruction is not programmed, the
value stored in D8000 is not valid until END processing.
M8005
Battery
voltage low
"Battery voltage low"
Y001
M8006 latches the battery voltage low.
0