B-18
5 Buffer Memory (BFM)
5.1 Assignment of Unit Numbers and Outline of Buffer Memory
FX
3U
/FX
3UC
Series PLC User's Manual - Analog Control Edition
FX3UC-4AD (4-channel Analog Input)
5. Buffer Memory (BFM)
This chapter describes the buffer memory incorporated in 4AD.
5.1 Assignment of Unit Numbers and Outline of Buffer Memory
1. Assignment of unit numbers
When special function units/blocks, such as 4AD, are connected to the main unit, unit numbers will be
sequentially assigned to the connected units/blocks starting from the unit/block next to the main unit. Check
the unit number assigned to 4AD.
2. Outline of buffer memory
The analog signals input into 4AD will be converted into digital values and then stored in the buffer memory
incorporated in 4AD.
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 buffer memory of 4AD.
To read/write data from/into the buffer memory of 4AD, the buffer memory can be directly specified using
FROM/TO instruction or application 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 6.4.
FX
3UC
-32MT
-LT
Main unit
Input/output
extension
block
Special
function block
Special
function block
Input/output
extension
block
Special
function unit
Unit number: 0
(Incorporated
CC-Link/LT)
Unit number: 1 Unit number: 2 Unit number: 3
*1. Since the buffer memory direct specification function (U
\G
) can directly specify the buffer memory in the
source or destination area of the application command, programs can be efficiently created.
FX
3UC
Series PLC
Sequence
program
FX
3UC
-4AD
Buffer
memory
A/D
conversion
FX
3
UC
-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
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