How To Read/Write From/To Buffer Memory - Mitsubishi Electric MELSEC-F FX3U-J1939 User Manual

FX -J1939 User's Manual
3U
5.2

How to Read/Write from/to Buffer Memory

To read/write from/to buffer memory in the FX
instructions that directly specify the buffer memory.
FX /FX /FX5U/FX5UC PLC applicable software is required to perform direct specification of the buffer
3U 3UC
memory and bit specification of word devices.
For further information on applied instructions, bit specification of word devices, direct specification of buffer
memory or special function unit/block unit number, refer to following manual.
1. Direct specification of buffer memory (FX
When directly specifying the buffer memory, specify the following device in the source or destination area of
the applied instruction as follows:
*1
Unit No. (0 to 7 )
*1. Unit No. 2 to No. 16 is assigned when the CPU module is an FX5U/FX5UC.
1) Reading out BFM data to PLC (MOV instruction)
If the following program is created, 1 point of data will be read out from buffer memory BFM #30 of unit
No.1 to data register D10.
READ command
Buffer memory No.
2) Writing PLC data into BFM (MOV instruction)
If the following program is created, 1 point of data (H0001) will be written to buffer memory BFM #20 of
unit No.1.
WRITE command
2. FROM/TO instructions
1) FROM instruction (Reading out BFM data to PLC)
Use the FROM instruction to read the data from the buffer memory.
If the following program is created, 1 point of data will be read out from buffer memory BFM #30 of unit
No.1 to data register D10.
READ command
Buffer memory No.
2) TO instruction (Writing PLC data into BFM)
Use the TO instruction to write data to buffer memory.
If the following program is created, 1 point of data (H0001) will be written to buffer memory BFM #20 of
unit No.1.
WRITE command
Buffer memory No.
34
U \G
Buffer memory No. (0 to 32766)
FNC 12
MOV
Unit No.
FNC 12
MOV
Transfer source
FNC 78
K1
FROM
Unit No.
FNC 79
K1
TO
Unit No.
-J1939, use the FROM/TO instructions or the applied
3U
/FX /FX5U/FX5UC only)
3U 3UC
is substituted with a number
U1\G30 D10
H0001 U1\G20
K30 D10 K1
K20 H0001 K1
5 Allocation of Buffer Memories
5.2 How to Read/Write from/to Buffer Memory
Refer to Programming manual
Transfer result
Buffer memory No.
Unit No.
Number of transfer data points
Destination register
Number of transfer data points
Transfer source