Mitsubishi MELSEC-A Series Programming Manual page 285

7. APPLICATION INSTRUCTIONS
Execution
Conditions
Operation Errors
DFRO
Reads the (n3×2) words of data from the buffer memory address specified by n2 in
the special module/special block specified by n1 and writes the data to the
A1FXCPU beginning with the device number specified by (D).
Buffer memory in
the special module/
special block
n2
n2+1
FROM and DFRO instructions are executed every scan while the read instruction is
ON.
FROMP and DFROP instructions are executed only once at the rising edge (OFF →
ON) of the read instruction.
Read command
In the following cases, operation error occurs and the error flag turns on.
• Access to a special module/special block is not possible.
• n1 designation is other than 0 to 7
• When "n3" points which start with the device specified at (D) exceed the specified
device range.
REMARK
Set the order number of the special module/special block in question to "n1", counted from the
A1FXCPU.
A1FXCPU
Device number
specified by (D)
(n3 2)
words
ON
OFF
Executed
P
Special module/
Special block
Set 0 at n1
7 − 83
A1FXCPU
(n3 2) points
Executed
per scan per scan
Executed
only once
Expansion unit/
Expansion block
MELSEC-A
Executed
only once
Special module/
Special block
Set 1 at n1