MITSUBISHI ELECTRIC QJ71C24N - Manual (Page 158)

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MELSEC-Q
7 DATA COMMUNICATIONS USING BIDIRECTIONAL PROTOCOL
(b) Data length
This indicates the number of bytes or words for the data portion of the
message.
The unit of data length (words/bytes) is in accordance with the word/byte
units designation in GX Configurator-SC.
1) For data communication from the external device to the Q series C24
The Q series C24 checks the length of the data received.
When the reception is normal, the Q series C24 stores the receive data
in the receive data storage area of the Q series C24 buffer memory,
assigning the first byte as the lower byte (L).
2) For data communication from the Q series C24 to the external device
The length of the transmission data is the number of the transmission
data designated by the sequence program using the BIDOUT
instruction.
The Q series C24 sends this value as is from the lower byte (L).
(c) Data portion
This consists of an array of original one-byte data to be transmitted to the
external device side, which can handle 00
H
to FF
H
code data.
1) For data communication from the external device to the Q series C24
If the receive data portion is normal, the Q series C24 takes the codes
as is and stores them in the receive data storage area in sequence,
beginning with the youngest address.
The storage size is in accordance with the data length in the message
(See item (b) above) and the word/byte units designation in GX
Configurator-SC.
2) For data communication from the Q series C24 to the external device
The transmission data portion is the number of the transmission data
designated by the sequence program using the BIDOUT instruction.
The Q series C24 sends the transmission data using the existing codes
until the transmission data count is reached in accordance with the
word/byte units designation in GX Configurator-SC to the transmission
data designation area.