Mitsubishi MELSEC LJ71C24, User Manual

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10 DATA COMMUNICATION USING THE NONPROCEDURAL PROTOCOL
10.3 Data Communications Precautions
The following describes the precautions to be taken during nonprocedural protocol
data communications.
(1) The C24 transmission sequence initialization conditions
The initial status indicates the status where transmission has stopped and
receive data has been discarded.
The C24 transmission sequence initialization conditions are as follows.
1) When the power is turned on, the CPU module is reset, or the C24 mode is
switched
2) When the receive data was cleared.
3) When the CD(DCD) signal was turned off when data communications were
performed by setting CD terminal check enable during full-duplex
communications through the RS-232 interface.
(2) Generation of framing error in external device
When nothing is transmitted from the C24 to the external device through the RS-
422/485 interface, a framing error may be generated by the noise etc, in the
external device.
Send an arbitrary code to identify the head of the send data from the C24 to the
external device.
Before data communication check the C24 interface specifications.
(3) Data communications with external device over a multidrop link
When the external device and the CPU module are connected by a 1:n multidrop
link, each C24 receives the data transmitted by the external device.
With a multidrop link, receive data by user frame ( 1).
If data is not received by user frame, create a sequence program that ignores
(discards) the receive data other than the receive data addressed to the host
station, including the data indicating the target CPU module in the message.
STX Space
Station
No. 0
CR LF
(02
H
) (20
H
) (32
H
) (32
H
) (0D
H
) (0A
H
)
(Example)
Station
No. 2
Data length
(BIN data)
Data
1 Refer to the User's Manual (Application).