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Devices in Detail
What happens when the PLC is switched off or stopped
In addition to the normal registers whose contents are lost when the PLC is stopped or the
power supply is turned off, the FX PLCs also have latched registers, whose contents are
retained in these situations.
NOTE
When special relay M8033 is set the contents of the unlatched data registers are also not
cleared when the PLC is stopped.
Data register overview
Device
Device identifier
Device type (for setting and polling)
Possible device values
Device address format
Number of devices and
addresses
You can also configure these registers as latched registers with the PLC parameters.
You can also configure these registers as unlatched registers with the PLC parameters.
If the optional battery is installed, the function of latched registers can be assigned to these registers in the PLC
parameters. They are then buffered by the battery.
4.5.2
Special registers
Just like the special relays (Chapter 4.2.1) starting at address M8000 the FX controllers also
have special or diagnostic registers, whose addresses start at D8000. Often there is also a
direct connection between the special relays and special registers. For example, special relay
M8005 shows that the voltage of the PLC's battery is too low, and the corresponding voltage
value is stored in special register D8005. The following table shows a small selection of the
available special registers as examples.
Special
register
D8004
D8005
D8010
D8013–D8019
D8030
D8031
FX Beginners Manual
Normal registers
D
Word device (two registers can be combined to store double-word
values)
16 bit registers: 0000
32 bit register: 00000000
Decimal
FX
128 (D0–D127)
1S
FX
128 (D0–D127)
1N
FX
2N
200 (D0–D199)
FX
2NC
FX
3G
128 (D0–D127)
FX
3GC
6900 (D1100–D7999)
FX
3GE
128 (D0–D127)
FX
3S
2744 (D256–D2999)
FX
3U
200 (D0–D199)
FX
3UC
Function
Error relay address (shows which error relays are set)
Battery voltage (e.g. the value "36" means 3.6V)
Current program cycle time
Time and date of the integrated real-time clock
Value read from potentiometer VR1 (0 – 255)
Value read from potentiometer VR2 (0 – 255)
Data register types
Latched registers
to FFFF
(-32768 to 32767)
H
H
to FFFFFFFF
(-2 147 483 648 to
H
H
2 147 483 647)
128 (D128–D255)
7872 (D128–D7999)
312 (D200–D511)
7488 (D512–D7999)
972 (D128–D1099)
128 (D128–D255)
312 (D200–D511)
7488 (D512–D7999)
Program processing
options
Read register contents
Read register contents
Change register contents
Read register contents (FX
FX
, FX
1N
FX
only)
3S
Registers
,
1S
, FX
and
3G
3GE
4 – 13
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