6.
DATA COMMUNICATIONS USING AN
M
:
N MULTIDROP LINK
-
MELSEC-A
(3)
Each computer without the access right checks the access
right
time
(the maximum data communications time) of the computer with the
access right and ignores incoming data which is addressed to others.
When the access right time exceeds the maximum data communica-
d
tions time, each computer executes the processing mentioned
in
(7).
II
!
.-
i
..
..
,.
--'
1
t
+
:
Computer with the access right
number
8OH)
number
SSH)
(station
number
81
H)
(4)
The computer that has finished data communications with
PC CPUs
and
the computers that
do
not need data communications
with
PC CPUs
transmit the access right transfer data to the computer at the next
station number.
u
When a computer is unable to receive a response message from the
next computer to which the access right is to be transferred,
it
keeps
on
transmitting the access right transfer data to the following com-
puters
in
the order of station numbers until the access right transfer is
completed.
7
-
J
7
(5)
The computer to which the access right is given transmits a response
message to the computer that gave the access right.
-J
(An
example of data communications using dedicated protocol
1)
7
*1
Computer
to
which
the
acE1188
right
is
transferred
(81
H)
(6)
The computer that transmitted a response message and obtained the
access right executes the processing mentioned
in
(2).
7
6-6
a
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