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CABLING THE COM20051
The COM20051 supports several types of cables
and cable interfaces in either bus or star
topologies.
The
following
is
a
list
of
media
transceivers,
supported
media,
and
supported topologies:
TRANSCEIVER
ALLOWED
TOPOLOGIES
MAX.
DIST.
MAX.
NODE
ISOLATION
VOLTAGE
SUPPORTED
MEDIA
HYC9068
Star only
2000ft.
N/A
<500V
Coax
HYC9088
Bus or Star
1000ft.
(Coax)
400ft.
(TP)
8
10
<500V
Coax
Twisted
Pair (TP)
RS-485
Bus
900ft.
32
15V
D.C.
Coupled
Twisted Pair
Isolated
RS-485
Bus
700ft.
12
2.5KV
Twisted
Pair
Fiber-Optic
Star
3Km
N/A
>2.5KV
Fiber
Note: The above figures are for a 2.5 Mbps data rate. Changing the data rate can significantly
increase or decrease the line length and node count.
For more information please refer to TN7-5 RS-485 Cabling Guidelines for the COM20020 Universal
Local Area Network Controller (ULANC) and Experimental Procedure for Verifcation of RS-485 Cabling
Guidelines or Cabling Alternatives for the COM20020, COM90C66, and COM90C165.
Compatability Considerations
Compatability with existing ARCNET installations
is
of
importance
to
some
designers.
The
COM20051 is compatible with older ARCNET
installations when it is operated in dipulse
mode
at
2.5
Mbps
using
normal
timeout values.
It is suggested that the
HYC9068 or HYC9088 transceivers be used to
maintain compatability. The COM20051 is not
compatible with standard ARCNET systems
when the device is used in backplane mode,
when the reduced timeout features are enabled,
or at data rates other than 2.5 Mbps.
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