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10. COMMUNICATIONS IN THE BIDIRECTIONAL MODE
MELSEC-A
(3)
Data area
The data of OOH to FFH code can be processed in a string of 1-byte data
as the send data.
(a) Data send from an AlSJ71C24 to a computer
The data area to be transmitted is the value written to the send data
storage area of the AlSJ71C24 buffer memory by the TO instruction
in a sequence program.
The AlSJ71C24 transmits the data according to the designated
length and bytelword units sequentially from the lower address in
unchanged codes.
(b) Data send from a computer to an AlSJ71C24
The data area received is written to the received data storage area
sequentially from the lower address in unchanged codes as they are
received.
The data length to be written is determined by the data length in the
received message and the designated wordlbyte units.
(4)
Check sum
The check sum is the lower 2 bytes (16 bits) of the result obtained by
adding the data length and the data area in the message as binary data.
If the setting at address 115H is
" I " , the check sum is not required.
(a)
Data send from an AlSJ71C24 to a computer
The AlSJ71C24 calculates and adds the check sum.
If the check sum is not processed, the check sum is not transmitted.
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