Functions And Operation Examples Of File Registers - Mitsubishi Electric FX3G SERIES Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
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 PLC power 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 PLC power 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.
Inside built-in memory
memory cassette
D1000
500 points ×
14 blocks
maximum
(7000 points
maximum)
• 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.
Instruction
BMOV instruction
Applied
instructions other
than
BMOV
instruction
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.
• When a file register is monitored from peripheral equipment, the data register area [B] inside the data memory is
read.
When "file register device current value change", "file register device forced reset" or "PLC memory all clear" is
executed from peripheral equipment, the file register area [A] inside the program memory is changed, and then the
data is automatically transferred to the data register area [B].
Accordingly, when file registers are to be overwritten, the program memory should be "built-in memory" or "memory
cassette whose protect switch is set to OFF". (The memory cassette cannot be overwritten from peripheral
equipment if its protect switch is set to ON.)
or
Program
memory
When power
is turned ON
Program/
When PLC
comment
mode is
changed D1000
from STOP
File register
to RUN
[A]
D7999
The remaining area can be used as data registers for general purpose.
Transferred contents
Data can be read from and written to the file register
area [A] inside the program memory.
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.
Inside system
RAM
D 0
Data
memory
Data register
For devices D1000 and later specified
as operands in applied instructions other
than BMOV (FNC 15) , indirectly
Data register Write
specified values for timers, counters or
[B]
devices in RST instructions can be read
from and written to the data register
Read
area [B] in the same way as general
Data register
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.
4 Devices in Detail
4.9 Data Register and File Register [D]
Remarks
−
1
2
3
4
5
6
7
8
9
10
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