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FX Series Programmable Controllers Devices in Detail 4
4-35
4.12.2 Battery Backed/ Latched Registers
Once data is written to a batter
y
backed re
g
ister, it remains unchan
g
ed until it is overwritten.
When the PLC’s status is chan
g
ed from RUN to STOP, the data in these re
g
isters is retained.
The ran
g
e of devices that is batter
y
backed can be chan
g
ed b
y
ad
j
ustin
g
the parameters of the
PLC. For details of how to do this please refer to the appropriate pro
g
rammin
g
tools manual.
Using the FX
2
-40AW/AP:
• When usin
g
an FX with either the FX2-40AWor the FX2-40AP a proportion of the latched
data re
g
isters are automaticall
y
assi
g
ned for communications use b
y
the FX2-40AW/AP
module.
Communication between Master and Slave 100 points M800 to M899
10 points D490 to D499
Communication between Slave and Master 100 points M900 to M999
10 points D500 to D509
4.12.3 Special Diagnostic Registers
Special re
g
isters are used to control or monitor various modes or devices inside the PLC. Data
written in these re
g
isters are set to the default values when the power suppl
y
to the PLC is
turned ON.
- Note: When the power is turned ON, all re
g
isters are first cleared to 0 (zero) and then the
default values are automaticall
y
written to the appropriate re
g
isters b
y
the s
y
stem
software. For example, the watchdo
g
timer data is written to D8000 b
y
the s
y
stem
software. To chan
g
e the settin
g
, the user must write the required value over what is
currentl
y
stored in D8000.
Data stored in the special dia
g
nostic re
g
isters will remain unchan
g
ed when the PLC is
switched from STOP mode into RUN.
Use of diagnostic registers:
• On no account should unidentified devices be used. If a device is used, it should onl
y
be
for the purpose identified in this manual. Please see chapter 6 for tables containin
g
data
and descriptions of the available devices for each PLC.