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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
15 External FX I/O Device – FNC 70 to FNC 79
15.9 FNC 78 – FROM / Read From A Special Function Block
15.9 FNC 78 – FROM / Read From A Special Function Block
Outline
This instruction reads the contents of buffer memories (BMF) in a special extension unit/block attached to a PLC.
When a large capacity of buffer memory (BFM) data is read by this instruction, a watchdog timer error may occur.
When bad effect is not given to the control even if data to be read is divided, use RBFM (FNC278) instruction.
→ For RBFM (FNC278) instruction, refer to Section 31.1.
1. Instruction format
2. Set data
3. Applicable devices
Explanation of function and operation
1. 16-bit operation (FROM and FROMP)
→ For the common items between FROM instruction and TO instruction,
refer to Subsection 15.9.1.
Special extension unit/block (BFM) → PLC (word device)
"n"-point 16-bit data starting from the buffer memory (BFM) # m2 inside a special extension unit/block No. m1 are
transferred (read) to "n"-point 16-bit data starting from inside a PLC.
Operand Type Description Data Type
m1
Unit number of a special extension unit/block
(K0 to K7 from the right side of the main unit)
16- or 32-bit binary
m2 Transfer source buffer memory (BFM) number 16- or 32-bit binary
Transfer destination device number 16- or 32-bit binary
n Number of transfer points 16- or 32-bit binary
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
3333333 333
n 33 33
P
FNC 78
FROM
D
16-bit Instruction
9 steps
Mnemonic Operation Condition
Continuous
Operation
Pulse (Single)
Operation
FROM
FROMP
DFROM
DFROMP
Mnemonic Operation Condition
32-bit Instruction
17 steps
Continuous
Operation
Pulse (Single)
Operation
D
D
D
Command
input
FNC 78
FROM
m1 m2 n
Unit No.
m1 = 0 to 7
Transfer source BFM #
(Special extension unit/block)
m2 = 0 to 32766
Transfer destination (PLC)
Number of transfer points
n = 1 to 32767
D