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6.
BIDIRECTIONAL
PROTOCOL
COMMUNICATIONS
MELSEC
QnA
6.1
Bidirectional Protocol Format and Data Setting Items
The following describes the control procedure and the contents of the setting items designated
with the control procedure when using the bidirectional protocol basic format to send and receive
data.
6.1.1
Control procedure and message structure
Data transmission from PC CPU to external device
Transmission order
e
External device
1 1 1
(When
abnormal)
(When normal)
I
I
\
QC24
E
Data
Data
Chfcksum
E
length
End of Transmission
\
WnO)
Request to Send
x
WnO)
I
""
rocessin
Data reception from external device at PC CPU
QC24
fl
(When normal)
Request to Read
Wn3)
End of Read
Wnl)
rocessin
6 - 2
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