10.
COMMUNICATIONS
IN
THE
BIDIRECTIONAL MODE
MELSEC-A
10.1
Bidirectional Mode Basic8
(1) What bidirectional mode means
PC CPU
(Sequence
program)
Write
c
(To*-
Send
request
signal
ON
i
PC CPU
(Sequence
program)
In bidirectional communications:
The bidirectional receivebend area
in
an AJ71C24 buffer memory is
used for data commuications with a computer.
The data written to an AJ71C24 buffer memory by the TO instruction in
a sequence program is transmitted to a computer in the same code with
the control code
(ENQ=OSH)
prefixed
to
the data to be transmitted.
AJ71
C24
buffer memory
(WHtoFFH)
I
A
I
Error
I
code
An AJ71C24 receives a response from a computer.
The data received from a computer is stored in an AJ71C24 received
area and read by the
FROM
instruction
in
the sequence program (the
data received is transferred in the code as received).
The response data is transmitted to a computer in response to the read
completed signal.
BidhdiondmOde
(OOH
to
FFH)
I
I
sum
I
Y
P
c
c
I
c
II
.
.
10-2
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