6.
DATA COMMUNICATIONS USING AN
M
:
N
MULTIDROP
LINK
MELSEC-A
6.2
Condition8 for
Computer
interlock
When constructing an m
:
n multidrop link using computers and
PC CPUs,
all computers must be interlocked to prevent several computers from simul-
taneously communicating with
PC CPUs.
This section explains how to interlock computers to allow data communica-
tions between a computer and a
PC CPU.
The term ‘interlocking‘ used in
this section means the procedure which provides a computer priority to use
a communications line. This priority is called an ‘access right’.
7
d
6.2.1
Computer
.trtion
number
allocation
For data communications with a designated computer, allocate
a
station
number within the range
of
128
to
159 (80H
to
9FH)
to each computer.
Set the station number for broadcasting to all computers at
160 (AOH).
Example: m
:
n
=
5
:
27
(
)
shows each station number of a computer and an
AJ71C24.
(Decimal: hexadecimal)
(128
:
8oH)
(129
:
81H)
Fl
(132
:
84H)
Y
I
I
Ij
ys”
1
.d
,
_,.
a
6-2
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