COM20020D datasheet(18/72 Pages) SMSC

18 / 72 page

Backplane Configuration

The Backplane Open Drain Configuration is

recommended for cost-sensitive, short-distance

applications like backplanes and instrumentation.

This mode is advantageous because it saves

components, cost, and power.

Since the Backplane Configuration encodes data

differently

than

the

traditional

Hybrid

Configuration,

nodes

utilizing

the

Backplane

Configuration cannot communicate directly with

nodes

utilizing

the

Traditional

Hybrid

Configuration. The Backplane Configuration does

not isolate the node from the media nor protects it

from Common Mode noise, but Common Mode

Noise is less of a problem in short distances.

The

COM20020D

supplies

programmable

output driver for Backplane Mode operation.

push/pull or open drain driver can be selected by

programming the P1MODE bit of the Setup 1

The COM20020D defaults to an open drain

output.

The Backplane Configuration provides for direct

connection between the COM20020D and the

media. Only one pull-up resistor (in open drain

configuration of the output driver) is required

somewhere on the media (not on each individual

node). The nPULSE1 signal, in this mode, is an

open drain or push/pull driver and is used to

directly drive the media.

It issues a 200nS

negative pulse to transmit a logic "1". Note that

when

used

the

open-drain

mode,

the

COM20020D does not have a fail/safe input on

the RXIN pin.

The nPULSE1 signal actually

contains a weak pull-up resistor.

This pull-up

should not take the place of the resistor required

on the media for open drain mode.

COM20020D Datasheet(PDF) 18 Page - SMSC Corporation

COM20020D Datasheet(HTML) 18 Page - SMSC Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72

Datasheet Download

Link URL