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4. COMMUNICATIONS USING A DEDICATED
PROTOCOL
MELSEC
QnA
1411
Summary of on-demand function data communications
PC CPU
Buffer
memory
3
Data
wrlte
When X0 is turned
ON, the PC CPU
executes the
on-demand function
Ion-demand functlon start/
PLS M1
@
End of ransrnlsslon
and sends data.
-
@) When the PC CPU writes data to the QC24 buffer memory with the TO instruction and
turns ON the on-demand request to send signal ("SO), the on-demand transmission
executing signal (X82) is turned ON.
@
The QC24 converts the written data to ASCII code and sends it to the external device.
@
When the QC24 finishes sending the data, it turns
OFF
the on-demand transmission
executing signal (X82).
@
When the external device receives the data, it executes the interrupt processing rou-
tine gram and displays the receive data.
Send data
(binary code)
QC24
"1 2 3 4 5 6
7
a"
4
(ASCII code)
PC CPU
Sequence
program
Step
0
QC24
I I
01
I t
I
\
On-demand transmisslon
result
X8OK81
On-demand transmlssion
executing
X82
I
I
I
I
External device
4
-
42
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