Table of Contents
Advertisement
10.
COMMUNICATIONS IN THE BIDIRECTIONAL MODE
MELSEC-A
10.8
Receiving Data in the Bidirectional Mode (Computer
+
AlSJ71C24)
Data receive area
The AlSJ71C24 stores the received data length and the received data
in the data receive area.
With a default setting, 80H to FFH in the buffer memory is allocated as
the data receive area.
This area may be changed as needed. Section 7.4.5 gives procedure
for changing the data receive area.
The unit of received data length
d e ~ e n d s on the settina at address
Buffer memory
[
1 0 3 ~ of the word/byte-setting area.
Addresses
Received data length storage area
(default)
the data length in the received
. . . . . - - . . . . -
message.
80H
is stored.
81H
receive
to
data
Send data
Received data storage area
FFH
Received data is stored sequentially
a
from the lowest address.
If the length of the data area in the message transmitted from the
computer is greater than the received data storage area (default: 127
words), split the data area into several blocks so that its length is smaller
than the received data storage area and append the block number to
specify each data area block.
Message format example:
4
Data area
Data
length
L
I
H
(2)
Reading received data
The AlSJ71C24 makes a read request t o the AISCPU at the following
timing (the timing at which the X l A l signal in the program example in
(4) is turned on).
Block
;
Data
No.
;
L
I
H
I
When the data length in the message and the set data length (bytes
or words as set in address 103H) have been received.
Check
sum
L
i n
If the check sum is processed, when the check sum has been
received with the above mentioned data area.
Example:
Wordlbyte setting: Word units
Data length in message: 10
In this case, the AlSJ71C24 makes a read request t o the the
sequence program at the time 10 words of data (plus the check
sum) have been received.
When the read request (Xnl) for the received data is made read the
data length and that length of data with a FROM instruction in a
sequence program and turn OFF the received data read completed
signal (Y (n+l)l).
Advertisement
Table of Contents
