IO.
COMMUNICATIONS
IN
THE
BIDIRECTIONAL
MODE
MELSEC-A
10.2
Handshake Signals and
Buffer
Memory
(1)
Handshake signals in the bidirectional mode
Signals known as
I/O
handshake signals are required for communica-
tions in the bidirectional mode.
These signals output data received from the sequence program to a
computer
or
detect signals from an external device to enable the
sequence program
to
read them.
Signal Timing
Y
(n+t)O
(s.nd
Tumd
OFF
by
program
rquw
Turned
ON
by
program
XnO
(Send
=mPMW
Turned
ON
by
U71C24
Xnl
(Reoeied
Turned
OFF
by
AJ71C24
Computer
pccpu
4
Turned
--@i
ON
by
U71Q4 OFF
by
pl0gr.m
Y
(n+r)
1
date
rw"d)
(*eke
IVd
dab
read
complete)
Turd ON
by
program
The number 'n' appended to
X
and
Y
is determined according to the
position where the
AJ71C24
is loaded and the number of
I/O
modules
loaded prior to this module.
If
this module
(AJ71C24)
is
loaded at slot
0
in a base module, XnO is expressed as
'XO'.
10-4
c
c
1
L
,-.-
'-
-
a
L
b
i
L
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