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6. DATA COMMUNICATIONS USING AN M
: N MULTIDROP LINK
MELSEC-A
(5) A slave station that has finished data communications with PC CPUs
transmits the communications completed code to the master station.
An example of the message format is shown in (6) below.
Slave stations which are not performing data communications with PC
CPUs check the transmission of the communications completed code.
During this checking, the slave stations must not perform data com-
munications with the master station.
(6) The master station that received the communications completed code
transmits a response t o the slave station that transmitted the com-
munications completed code.
(An example of data communications using dedicated protocol 1)
(7) After the processing given in
(6)
is completed or when the access right
time of a slave station with the access right exceeds the maximum data
communications time:
Slave station
message
*1
(a) The master station waits for a communications request from a slave
station.
computerthat
B
wants the
WH)
When the master station receives a communications request, the
processing mentioned in
(2)
is executed.
(b)
Until data communications with PC CPUs is required, a slave station
does not perform data communications with the master station.
90
desired symbol far the
A
Flbrn
Master station
c
station
station
communications com-
computer (80H)
K
number
number
pleted code.
I81Hl
I82Hl
06H
3 8 H I r n
3 8 H 1 3 2 H
[6] message
f o
~ r b m
I
I
'1 The command symbol
When data communications with PC CPUs is required, the process-
ings in and after
(1)
are executed.
'P
in this example is
indicated only for ex-
planation. Use any
N
Q
05n
stetion
"umber
IBOH)
38ni33H
station
number
l82H)
38H132H
command
IM
Message
wait t i m e
(21
32H
sum
check
code
@7Hl
4 2 H 1 3 M
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