COM20051I Datasheet, PDF (64/74 Pages) SMSC Corporation – Integrated Microcontroller and ARCNET (ANSI 878.1) Interface

CABLING THE COM20051I
The COM20051I 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:
ALLOWED
TRANSCEIVER TOPOLOGIES
HYC9068
HYC9088
Star only
Bus or Star
RS-485
Bus
MAX.
DIST.
2000ft.
1000ft.
(Coax)
400ft.
(TP)
900ft.
MAX.
NODE
N/A
8
10
32
Isolated
RS-485
Bus
700ft.
12
Fiber-Optic
Star
3Km
N/A
ISOLATION
VOLTAGE
<500V
<500V
15V
D.C.
Coupled
2.5KV
>2.5KV
SUPPORTED
MEDIA
Coax
Coax
Twisted
Pair (TP)
Twisted Pair
Twisted
Pair
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 COM20051I 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 COM20051I 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.
SMSC DS – COM20051I
Page 64
Rev. 03/27/2000