Mitsubishi Melsec-L Series User Manual page 26

(3) Nonprocedural protocol
(4) Bidirectional protocol
When receiving data
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Fixed or variable length messages can be received in accordance with the
external device specifications.
Nonprocedural protocol enables communication between an external device and
the CPU module by freely setting the data format and transmission control
procedures.
It is used for the data communication using the protocols of external devices,
such as measuring instruments, barcode readers, etc.
The bidirectional protocol enables communication between an external device
and the CPU module using the data format and communication control
procedures for the bidirectional protocol.
Use this protocol to check if the communication is successfully completed.
The data communication is performed as follows.
1) External device sends data to the C24
Data
ENQ
length
When normal
When abnormal
2) The C24 notifies whether the data
communication has been completed
normally by a response message.
1 SERIAL COMMUNICATION MODULE FUNCTIONALITY
Send
Any data
Any data
Receive
Sum
Any data check
code
ACK
Error
NAK
code
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