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10. COMMUNICATIONS IN THE BIDIRECTIONAL MODE
MELSEC-A
10.7 Basic Program to ReadIWrite Buffer Memory
The following describes a basic sequence program to bidirectional read and
write data to and from the AJ71C24 buffer memory.
(1)
Reading data from the receive area (FROM, FROMP. DFRO, DFROP)
Data is read from the buffer memory bidirectional receive area (default:
80H to FFH).
PC
CPU
AJ71
C24
Buffer memory (bidirectional receive area)
(1)
xnl
(Received data read requesl)
r-
-
y,,,+,,l
(Received data read completed)
(4)
L -
(1) Read request
( ' )
Received data length
read
Reads the received data length from the no-protocol received
data length storage area
o f
buffer memory when the read request
signal V n l ) is turned
ON.
MOVP
1
D
1
Z
Stores the read data length to the index register
(2)
Turns
ON
the read completed signal (Y(n+l)l) alter the recieved
data has been read
(3) Received data read
4
FROMP
1
1
n2
I
I
1 -
(4)
Read completed
*
Data read by program (3) is processed as the recieved data.
Readsthe received data of the read received data length from the
received data storage area of buffer memory.
Example:
To read the data of ( n + l ) words from the area, beginning with
buffer memory address 80H, to the area beginning with DO when the
AJ71C24
1 1 0
numbers are allocated to 130 to 14F (unit: word).
r - - - - - - - - - - -
From buffer memory
-
-
- - - - -
-
-
-
- - - -
Received
data
-
-
- - - - -
From buffer memory
(area beginning with 81 H)
Y141
- - -
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