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8.
COMMUNICATIONS USING DEDICATED PROTOCOLS
MELSEC-A
(3)
On-demand request processing timing chart
(a) Full-duplex communications
Computer is transmitting data
On-demand function executing
(1)
Xn3
A ~ S C P U TO instruction to buffer memory
addresses 109H and 10AH
x
1) The on-demand function executing signal (Xn3) turns ON imme-
diately and
,
the on-demand data is transmitted when the on-
demand request is made.
2) Transmission of response data (beginning with STX) to the com-
mand data (beginning with ENQ) is suspended until the comple-
tion of on-demand data transmission.
l ~ o m p u t e r is receiving dz
On-demand
1
data
On-demand function executing
Xn3
A ~ S C P U
TO instruction to buffer memory
'
addresses 109H and 1 OAH
The on-demand function executing signal (Xn3) turns ON imme-
diately when the on-demand request is made.
Transmission of the on-demand data is suspended until the
completion of the response data (beginning with STX) to the
command data (beginning with ENQ).
Transmission of the response data (beginning with ACK) from the
computer in response to the response data (beginning with STX)
from the AlSJ71C24 is possible while the on-demand data is
received.
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