Mitsubishi Electronics FX3G User Manual

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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 function 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 function 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
X Y M T C S D .b KnX KnY KnM KnS T C D R U \G
V Z Modify K H
E
" "
P
m1
m2
n
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 ‚