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10. COMMUNICATIONS IN THE BIDIRECTIONAL MODE
MELSEC-A
10.9
Transmitting Data In the Bldirectlonal Mode (AJ71C24
- ,
Computer)
Transmitting means outputting data which was written to the bidirec-
tional mode send buffer memory area (hereafter referred to as the send
area), from the AJ71C24 to a computer in response to turning ON the
PC CPU send request signal (Y(n+l)O).
(1) Send area and writing send data
The send data length and send data are written to the send area.
(a) The length of data to be written (having been written) to the bidirec-
tional send data length storage area in either words or bytes.
(b) The data to be transmitted is written to the send data storage area.
When the send request signal (Y(n+l)O) is turned ON after (a) and
(b) have been executed, the AJ71C24 transmits the designated
length of designated data from the send data storage area sequen-
tially from the lower address.
By default, the buffer memory area O H to 7FH is allocated to the
send area.
This area may be changed as needed. Section 7.4.4 gives the
procedure for changing the send area addresses.
The unit of send data length
-. . . . .
depends on the setting at address
103H of the word/byte setting
area.
Addresses
(defaun)
O H
1H
to
7FH
Buffer memory
Send data length storage area
Designate the length of data to be
sent with the TO instruction.
Designated value is transmitted as
the data length.
Send data storage area
Send data is transmitted sequentially
from the lowest address.
Send
area
Send data length
------.......
Send data
- - - - . .
P----
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