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5 Buffer Memory (BFM)
5.1 Assignment of Unit Numbers and Outline of Buffer Memory
A
Common Items
B
FX
3U
-4AD
FX
3UC
-4AD
C
FX
3U
-4AD-ADP
D
FX
3G
-2AD-BD
E
FX
3U
-4DA
F
FX
3U
-4DA-ADP
G
FX
3G
-1DA-BD
H
FX
3U
-3A-ADP
I
FX
3U
-4AD-PT
-ADP
J
FX
3U
-4AD-PTW
-ADP
FX
3G
/FX
3U
/FX
3UC
PLC User's Manual - Analog Control Edition
FX3U-4AD/FX3UC-4AD (4-channel Analog Input)
2. Outline of buffer memory
The analog signals input into the 4AD will be converted into digital values and then stored in the 4AD buffer
memory.
To switch the input mode between voltage input and current input, or to adjust the offset or gain, numeric data
will be sent from the main unit and written/set in the 4AD buffer memory.
To read/write data from/to the 4AD buffer memory, the buffer memory can be directly specified using the
FROM/TO instruction or an applied instruction. Using this function, sequence programs can be easily created.
→ For a detailed description of buffer memory reading/writing, refer to Section 5.2.
→ For a detailed description of the buffer memory, refer to Section 5.4.
*1. Since buffer memory direct specification (U\G) can directly specify the buffer memory in the source or
destination area of an applied instruction, programs can be created efficiently. (This function is supported
only in FX
3U/FX3UC PLCs.)
Main unit
Sequence
program
4AD
Buffer
memory
A/D
conversion
4AD
Buffer
memory
A/D
conversion
Analog dataAnalog data
Digital
value
Digital
value
Flowmeter, pressure sensor, etc.
• TO instruction
• FROM
instruction
• BFM direct
specification
*1
• BFM direct
specification
*1
• TO instruction
• BFM direct
specification
*1
• FROM instruction
• BFM direct
specification
*1