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6. BIDIRECTIONAL
PROTOCOL
COMMUNICATIONS
MELSEC QnA
0
17
28
37
47
This section sends data from the PC CPU to an external device.
The send data count units are word units.
[Practice Contents]
When X0 is turned ON, the character data (ASCII code) [ABCDEFGH] is written to the QC24 buffer
memory (addresses 400H-404H).
When X1 is turned ON, the character data [ABCDEFGH] is sent to the external device using the
bidirectional protocol.
When the PC CPU receives a response from the external device, it ends transmission.
6.5.1
Sequence program
E/$l,ff[
$MOV "ABCDEFGH"
D l 1
[
MOV
K1
DO
[
MOV
KO
D l
[
MOV
K4
D2
[SET
MO
.
s
y70
ERST
MO
x1
m
[DTO
HE
HO
HOCOFFOOFF
K1
RST
Y70
[RST
Y71
F
. .
Stores the send data to D l 1
-.
E.
.
Designates the interface (CHI)
that is to send the data.
E.
. .
Clears the transmission result
storage deuce to zero.
E.
.
Send data count 4 words
F
D l 1 : Send data storage source
M1: Turned ON at the end
of
. . .
head device
execution of the instruction
E
' .
Normal end
E.
.
.
Abnormal end
(Dl =Error code storage)
v'
.
.
Error LED OFF request
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