Table of Contents
Advertisement
10. COMMUNICATIONS IN THE BIDIRECTIONAL MODE
MELSEC-A
10.8
Receiving Data i n the Bidirectional Mode (Computer
-.
AJ71C24)
(1)
Data receive area
The AJ71C24 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 changingthe data receive area.
Addresses
(default)
80H
81 H
to
FFH
Buffer memory
Send data length
- - - - - - - - - - - - -
Data
receive
data
Send data
The unit of received data length
depends on the setting at address
103H
of the wordlbyte setting area.
Received data length storage
area
the data length in the received
message.
is stored.
Received data storage area
Received data is stored sequentially
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:
(2)
Reading received data
The AJ71C24 makes a read request to the PC CPU at the following
timing (the timing at which the X I A I signal in the program example in
(4) is turned on).
*When the data length in the message and the set data length
(bytes or words as set in address 103H) have been received.
If the check sum is processed, when the check sum has been
received with the above mentioned data area.
Example:
Wordibyte setting: Word units
Data length in message: 10
In this case, the AJ71C24 makes a read request to 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 ) .
-1
Check
sum
L
#
H
-
Data area
,
I
Block
:
No.
;
Data
L
H
,
N
Q
I - ; - - -
1-
Data
length
L
,
H
Advertisement
Table of Contents
