106
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.8 Data Register and File Register [D]
4.8.4
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).
Combined two file registers can store 32-bit numeric data (whose most significant bit specifies the positive or
negative sign).
Fixed latched (battery backed) type data registers D1000 and later can be as file registers up to 7000 points
by a parameter.
• In parameter setting, 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 file registers D1000 and later are set as file registers, remaining registers can be used as
latched (battery backed) type data registers.
This paragraph explains how to handle file registers.
1. Operation of file registers
• The file register area [A] set inside the built-in memory or optional memory is 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.
The data register area [B] is latched (battery backed). When data registers are set as file registers by
parameters, however, the file register area [A] inside the program memory is transferred when the power of
the PLC is turned ON or when the PLC mode switches from STOP to RUN. In this case, the contents
changed in the data memory are initialized when the plc turns off and 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 difference regarding to file registers (D1000 and later) between BMOV (FNC 15)
instruction and other 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
except 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
Remaining area can be used as latched (battery backed) type data registers
for general purpose.
Devices D1000 and later specified as
operands in applied instructions except
FNC 15 (BMOV), indirectly specified
values for timers or 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.
