12 Program Example
12.1 Reading/Writing Buffer Memory
251
FX
3U
-20SSC-H Positioning Block User's Manual
11
Buffer
M
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12
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Exam
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13
D
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A
List
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V
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Infor
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12.1
Reading/Writing Buffer Memory
12.1.1
Assigned unit number
1. Assigned unit number
The unit number for the 20SSC-H is automatically assigned No.0 to No.7 starting from the special function
unit/block closest to the PLC main unit.
• In the FX
3U,
FX
3UC
(D, DS, DSS) series
• In the FX
3UC
-32MT-LT, FX
3UC
-32MT-LT-2
12.1.2
How to read/write from/to buffer memory
To read and write the buffer memory in the 20SSC-H, use the FROM/TO instructions or direct specification of
the buffer memory.
FX
3U
/FX
3UC
PLC applicable software is required to perform direct specification of the buffer memory and bit
specification of word devices.
→
For details of applied instructions, bit specification of word devices and direct specification of the
buffer memory, refer to the PROGRAMMING MANUAL
Note
Buffer memory that is assigned in 32 bits must use 32-bit instructions to read/write.
Data cannot be correctly read/written from/to buffer memory assigned in 32 bits if 16-bit read/write
instructions are used.
1. How to read and write numeric values
1) Direct specification of buffer memory
Specify the buffer memory directly as the source or destination in applied instructions, and then read or
write the contents of the buffer memory.
a) Reading and transferring numeric values to data registers
In the program below, the contents of the buffer memory (BFM #0 and #1) in unit No. 1 are read and
transferred to data registers (D10 and D11).
FX
3U
Main unit
Input/output
extension
block
Special
function block
Special
function block
Input/output
extension
block
Special
function unit
Unit No.0
Unit No.1
Unit No.2
, FX
3UC
(D, DS, DSS)
Input/output
extension
block
Special
function block
Special
function unit
Unit No.0
(built-in CC-Link/LT)
Unit No.1
Unit No.2
Unit No.3
FX
3UC
Main unit
-32MT-LT,
-32MT-LT-2
FX
3UC
Input/output
extension
block
Special
function block
Unit No. (0 to 7)
Buffer memory No. (0 to 15399)
U \G
is substituted with a
number
Read
command
FNC 12
DMOV
U1\G0
D10
Transfer
result
Unit No.
Buffer memory No.