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6. DATA COMMUNICATIONS USING AN M
:
N
MULTIDROP LINK
MELSEC-A
6.2
Conditions for Computer Interlock
When constructing an m : n multidrop link using computers and PC CPUs,
all computers must be interlocked t o prevent several computers from simul-
taneously communicating with PC CPUs.
This section explains how to interlock computers t o 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'.
6.2.1
Computer station number allocation
For data communications with a designated computer, allocate a station
number within the range of 128 to 159
(80H
to QFH) t o 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)
(132 : 64H)
Computer
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