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5 Buffer Memory (BFM)
5.2 Buffer Memory Reading/Writing Method
FX
3G
/FX
3U
/FX
3UC
PLC User's Manual - Analog Control Edition
FX3U-4AD/FX3UC-4AD (4-channel Analog Input)
5.2 Buffer Memory Reading/Writing Method
To read or write to the 4AD buffer memory, use the FROM/TO instructions or buffer memory direct
specifications
*1
.
However, to use buffer memory direct specification
*1
, software compatible with FX3U/FX3UC Series PLCs is
required.
*1. This function is supported only in FX
3U/FX3UC PLCs.
→ For a detailed description of software compatible with the FX
3U/FX3UC Series PLC,
refer to Section 1.4.
5.2.1 Buffer memory direct specification (FX3U, FX3UC PLC only)
When directly specifying the buffer memory, specify the following device in the source or destination area of
the applied instruction as follows:
1. Example 1
If the following program is created, data in buffer memory (BFM #10) of unit 1 will be multiplied by the data
(K10), and then the multiplication result will be output to data registers (D10, D11).
2. Example 2
If the following program is created, the value in data register (D20) is added to K10 and written to buffer
memory (BFM #6) of unit 1.
5.2.2 FROM/TO instruction (FX3G, FX3U, FX3UC PLC)
1. FROM instruction (Reading out BFM data to PLC)
Use the FROM instruction to read the data from the buffer memory.
In a sequence program, use this instruction as follows:
If the above program is created, 1 point of data will be read out from the buffer memory BFM #10 of unit No.1
to data register D10.
2. TO instruction (Writing PLC data into BFM)
Use the TO instruction to write data to a buffer memory.
In a sequence program, use this instruction as follows:
If the above program is created, 1 point of data (H3300) will be written to buffer memory BFM #0 of unit No.1.
Buffer memory number (0 - 6999)
U
\G
Enter a numeric value in
Unit number (0 to 7)
FNC 22
MUL
U1\G10 K10 D10
Multiplier
Multiplication result
Unit number
Buffer memory number
READ command
WRITE command
FNC 20
ADD
D20 K10 U1\G6
Addend
Augend
Unit number
Buffer memory number
Addition
result
( )
READ command
FNC 78
FROM
K1 K10 D10 K1
Destination register
Number of transfer
data points
Unit number
Buffer memory number
WRITE command
FNC 79
TO
K1 K0 H3300 K1
Transfer source
Number of transfer
data points
Unit number
Buffer memory number