145
FX
3G
/FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.10 Extension Register [R] and Extension File Register [ER]
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
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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
4.10.7 Cautions on using extension file registers
1. Cautions on writing data to extension file registers (FX
3U
/FX
3UC
PLC)
Because extension file registers are stored in the flash memory inside a memory cassette, pay attention to
the following points:
• When writing data to extension file registers by SAVER instruction
Initialize sectors to be written before executing this instruction. After initialization, store data to be written
to extension registers.
In FX
3UC
PLCs Ver.1.30 or later, it is not necessary to initialize sectors to be written when using RWER
instruction.
• When writing data to extension file registers by LOGR instruction
Initialize sectors to be written before starting to log data.
• When using INITR instruction
This instruction initializes the contents of specified extension registers and extension file registers.
When initializing only extension file registers by this instruction, make sure to temporarily move the
contents of extension registers to unused extension registers or unused data registers before executing
this instruction.
When initializing only extension file registers in FX
3UC
PLCs Ver.1.30 or later, use INITER instruction.
2. Initialization of extension file registers
Because the contents of extension file registers are stored in the memory cassette or built-in EEPROM, use
the data clear operation in a sequence program or GX Developer to initialize them.
For writing data to extension file registers in FX
3U
/FX
3UC
PLCs, it is necessary to initialize the target area to
be written in advance.
For writing data to extension file registers in FX
3G
PLCs, it is not necessary to initialize the target area to be
written in advance.
1) When initializing extension file registers in a program (required only in FX
3U
/FX
3UC
PLCs)
a) Initializing only extension file registers in sector units [Ver.1.30 or later]
Example: When initializing ER0 to ER4095 (initializing two sectors starting from ER0)
b) Initializing extension registers and extension file registers in sector units
Example: When initializing R0 to R4095 and ER0 to ER4095 (initializing two sectors starting from R0
and ER0)
2) When initializing extension file registers using GX Developer
Select [Online]
→
[Clear PLC memory...] in GX Developer, and clear [Data device].
This operation initializes the contents of timers, counters, data registers, file registers and extension
registers.
3. Allowable number of writes to the memory
Note the following cautions on access to extension file registers.
• In FX
3U
/FX
3UC
PLCs
Data can be written to the memory cassette (flash memory) up to 10,000 times.
Every time the INITR (FNC292), RWER (FNC294) or INITER (FNC295) instruction is executed, it is
counted as a write to the memory. Make sure not to exceed the allowable number of writes.
When a continuous operation type instruction is used, data is written to the memory in every operation
cycle of the PLC. For preventing this, make sure to use a pulse operation type instruction.
Execution of the LOADR (FNC290), SAVER (FNC291) or LOGR (FNC293) instruction is not counted as a
write to the memory. However, it is necessary to initialize the writing target sector before executing the
SAVER (FNC291) or LOGR (FNC293) instruction.
Every time the INITR (FNC292)or INITER (FNC295) instruction is executed, it is counted as a write to the
memory. Make sure not to exceed the allowable number of writes.
Command input
FNC 295
INITERP
R0
K2
The current value is initialized to "FFFF
H
" in ER0
to ER4095.
Command input
FNC 292
INITRP
R0
K2
The current value is initialized to "FFFF
H
" in R0 to R4095 and
ER0 to ER4095.