Mitsubishi MELSEC LJ71C24, User Manual

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11 DATA COMMUNICATION USING THE BIDIRECTIONAL PROTOCOL
11 DATA COMMUNICATION USING THE BIDIRECTIONAL PROTOCOL
This communication enables data transfer between an external device and a CPU
module using the data format and transmission control procedure for the bidirectional
protocol.
The feature of this data communication is that a response message is sent from the
data receiving side to the data sending side, informing if the communication was
completed.
Use this to check if the data communication was completed normally.
Sequence programs for sending and receiving data are required on the CPU module
side.
ENQ
Data
length
When receiving data
Any data
Sum
check
code
ACK
When normal
NAK
Error
code When abnormal
1) External device sends data to the C24
2) The C24 notifies whether the data
communication has been completed
normally by a response message.
POINT
Communication programs using the bidirectional protocol can be easily replaced
with those of the predefined protocol by the predefined protocol support function of
GX Works2.
With the predefined protocol, programs can be run only by starting communication
according to the specified protocol, and this can reduce the number of steps
considerably.
For the communication using the predefined protocol, refer to Chapter 9.
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