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FX3S/FX3G/FX3GC/FX3U/FX3UC Series
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.10 Extension Register [R] and Extension File Register [ER]
4.10 Extension Register [R] and Extension File Register [ER]
Extension registers (R) are the extended form of data registers (D).
The contents of extension registers (R) can be stored in extension file registers (ER). In FX
3U/FX3UC PLCs, extension
file registers (ER) are available only while the memory cassette is attached.
4.10.1 Numbers of extension registers and extension file registers
The table below shows numbers of extension registers (R) and extension file registers (ER).
(Numbers are assigned in decimal.)
1. FX3G/FX3GC PLCs
2. FX
3U/FX3UC PLCs
*1. These registers can be changed to the latched (battery backed) type by the parameter setting when the
optional battery is used. However, the latched range cannot be set.
*2. These registers are stored in the EEPROM built in the PLC, or in the EEPROM in the memory cassette when
the memory cassette is attached.
*3. Available only while a memory cassette is mounted (because they are stored in the flash memory inside a
memory cassette.)
4.10.2 Data storage destination and access method
Because the memory for storing data is different between extension registers and extension file registers, the access
method is different as shown in the table below:
Data storage destination
Difference in the access method
Extension register (R)
(General type)
Extension file register (ER)
(file type)
R0 to R23999
24000 points
*1
ER0 to ER23999
24000 points
*2
Extension register (R)
(latched [battery backed] type)
Extension file register (ER)
(file type)
R0 to R32767
32768 points
ER0 to ER32767
32768 points
*3
Device PLC Data storage destination
Extension register
FX3G/FX3GC Built-in RAM
FX3U/FX3UC Built-in RAM (latched [battery backed] area)
Extension file register
FX3G Built-in EEPROM or EEPROM in memory cassette
FX3GC Built-in EEPROM
FX3U/FX3UC Memory cassette (flash memory)
Access method
Extension
register
Extension file register
Reading in program
UOnly dedicated instructions are
enabled
Writing in program
UOnly dedicated instructions are
enabled
Display module
Data change
method
Test operation in online mode of GX Works2, GX Developer ×
Batch writing by GX Works2, GX Developer
Computer link function ×