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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
31 Data Transfer 3 – FNC275 to FNC279
31.1 FNC278 – RBFM / Divided BFM Read
31.1 FNC278 – RBFM / Divided BFM Read
Outline
This instruction reads data from continuous buffer memories (BFM) in a special function block/unit over several
operation cycles by the time division method. This instruction is convenient for reading receive data, etc. stored in
buffer memories in a special function block/unit for communication by the time division method.
FROM (FNC 78) instruction is also available to read the buffer memory (BFM) data.
→ For FROM (FNC 78) instruction, refer to Section 15.9.
1. Instruction format
2. Set data
3. Applicable devices
S: Except special data register (D)
Explanation of function and operation
1. 16-bit operation (RBFM)
"n1" buffer memory (BFM) units at location # "m2" in special function unit/block No. "m1" are read to in the PLC.
While transfering, "n1" is divided by "n2" so n1/n2 buffer memories (rounded up when there is a remainder) are
transferred per scan time.
→ For the unit No., buffer memory (BFM) #, cautions, and program example,
refer to Subsection 31.1.1.
• When the instruction is finished normally, the instruction execution complete flag M8029 turns ON. When the
instruction is finished abnormally, the instruction execution abnormally complete flag M8329 turns ON.
• When RBFM (FNC278) or WBFM (FNC279) instruction is executed in another step for the same unit number, the
instruction non-execution flag M8328 is set to ON, and execution of such an instruction is paused.
When execution of the other target instruction is complete, the paused instruction resumes.
Operand Type Description Data Type
m1 Unit number [0 to 7]
16-bit binary data
m2 Head buffer memory (BFM) number [0 to 32766]
Head device number storing data to be read from buffer memory (BFM)
n1 Number of all buffer memories (BFM) to be read [1 to 32767]
n2 Number of points transferred in one operation cycle [1 to 32767]
Oper-
and
Type
Bit Devices Word Devices Others
System User Digit Specification System User
Special
Unit
Index
Con-
stant
Real
Number
Charac-
ter String
Pointer
XYMTCSD
.b KnX KnY KnM KnS T C D R
U\G
V Z Modify K H E "
"P
m1 33 33
m2 33 33
S 33
n1 33 33
n2 33 33
FNC 278
RBFM
16-bit Instruction
11 steps
RBFM
Mnemonic Operation Condition
Continuous
Operation
−
Mnemonic Operation Condition
32-bit Instruction
D
D
D
Command
input
M
{{
M8029
FNC278
RBFM
m1 m2 D
n1 n2
M8328
M
Instruction execution
complete
Instruction
non-execution
Unit No. "m1"
BFM#(m2)
BFM#(m2+n1-1)
PLC
+n1-1
D
D
*1 "n2" buffer memories are read in
each operation cycle. Reading is
executed in "n1/n2" times. ("n1/n2"
is rounded up if it is not an integer.)
Read
*1
M8329
M
UU
Instruction execution
abnormally complete