135
FX
3G
/FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.9 Data Register and File Register [D]
1
Int
roduct
ion
2
O
ver
view
3
In
str
uc
tion
Li
st
4
D
evices
in D
etail
5
Spec
ified t
he
D
evice &
C
onst
ant
6
Bef
ore
Pr
ogr
am
m
ing
7
B
asic
In
st
ru
ct
io
n
8
FN
C
00-FN
C
09
P
rogr
am
F
low
9
FN
C
10
-FN
C
19
Mo
ve
&
Co
mp
are
10
FNC2
0-F
NC2
9
Ar
ith.
&
Logic
O
per
ation
4.9.4
Functions and operation examples of file registers
A file register is a device for setting the initial value of a data register with the same number.
Each file register stores 16-bit data (whose most significant bit specifies the positive or negative sign). Two
file registers combined can store 32-bit numeric data (whose most significant bit specifies the positive or
negative sign).
Up to 7000 data registers starting from D1000 can be specified as file registers by the parameter setting.
• In parameter settings, 1 to 14 blocks can be specified. One block secures 500 file registers, but uses the
program memory area by 500 steps.
• When some of data registers starting from D1000 are specified as file registers, the remaining data
registers not specified as file registers can be used as data registers.
This section explains how to handle file registers.
1. Operation of file registers
• The contents of the file register area [A] set inside the built-in memory or memory cassette are batch-
transferred to the data memory area [B] inside the system RAM when the power of the PLC is turned ON or
when the PLC mode switches from STOP to RUN.
When data registers are specified as file registers by the parameter setting, the contents of the file register
area [A] inside the program memory are transferred when the power of the PLC is turned ON or when the
PLC mode switches from STOP to RUN. This means that the contents changed in the data memory are
initialized every time when the PLC turns ON or when the PLC mode switches from STOP to RUN.
When it is necessary to save data changed in the data memory using a sequence program, update the file
register area [A] to the changed values by the same-number register update mode in BMOV
(FNC 15) instruction described later.
• Difference between BMOV (FNC 15) instruction and other instructions
The table below shows the differences between the BMOV (FNC 15) instruction and other applied
instructions.
The data stored in data registers set as file registers are automatically copied from the file register area [A]
to the data register area [B] when restoring the power.
Instruction
Transferred contents
Remarks
BMOV
instruction
Data can be read from and written to the file
register area [A] inside the program memory.
−
Applied
instructions
other than
BMOV
instruction
Data can be read from and written to the data
register area [B] inside the image memory in
the same way as general data registers.
Because the data register area [B] is provided
inside the system RAM in the PLC, its contents can
be arbitrarily changed without being limited by the
optional memory format.
Data register
[B]
Inside system
RAM
Inside built-in memory
or
memory cassette
Program
memory
Program/
comment
File register
[A]
D1000
500 points
×
14 blocks
maximum
(7000 points
maximum)
When power
is turned ON
When PLC
mode is
changed
from STOP
to RUN
Data
memory
Data register
Data register
D7999
D1000
D 0
Read
Write
The remaining area can be used as data registers for general purpose.
For devices D1000 and later specified
as operands in applied instructions other
than BMOV (FNC 15) , indirectly
specified values for timers, counters or
devices in RST instructions can be read
from and written to the data register
area [B] in the same way as general
data registers.
