Table of Contents
Advertisement
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 AlSJ71C24 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 t o FFH).
(1) Read request
Xnl
(Received data read request)
(1)
y ( , , + , , i
(Received data read completed)
. .
(2) Received data length read
Reads the received data length from the no-protocol received
I
FROMP
I
n l
I
n2
I
D
1
n3
data length storage area of buffer memory when the read request
signal (Xnl) is turned ON.
I
Stores the read data length to the index register (2).
(3) Received data read
Reads the received data of the read received data length from the
received data storage area of buffer memory.
(4) Read completed
Turns ON the read completed signal (Y(n+l)l) aflerthe recieved
data has been read
*
Data read by program (3) is processed as the recieved data.
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
AlSJ71 C24
I10
numbers are allocated to 130 to 14F (unit: word).
-------------
FROMP I H 1 3 1 ~ 8 1 1 D l ~ K O Z
From buffer memory
( 8 W
From buffer memory
(area beginning with 81H)
Advertisement
Table of Contents
