COM90C66 datasheet(44/76 Pages) SMSC

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those tokens transmitted by this node).

The RCVACT and TOKEN bits of the Diagnostic

Status

may

help

the

user

troubleshoot

the

network

the

node.

unusual events are occurring on the network, the

user may find it valuable to use the TXOFF bit of

the Configuration Register to qualify events.

Different combinations indicate different types of

problems.

Table 15 - Diagnostic Bits for Troubleshooting Network Activity

RCVACT

TOKEN

TXOFF

DESCRIPTION

NORMAL RESULTS

The node is not part of the network.

The

network is operating properly without this

node.

The node sees receive activity and sees the

token.

The basic transmit function is

enabled.

Network and node are operating

properly.

ABNORMAL RESULTS

The node sees receive activity, but is not

seeing the token. Perhaps no other nodes

exist on the the network, or some type of

data corruption exists, or the media driver is

not functioning properly, or the topology is

set up incorrectly, or there is noise on the

network, or a reconfiguration is occurring.

No receive activity is seen and the basic

transmit function is enabled. The transmitter

and/or receiver are not functioning properly.

No receive activity is seen and the basic

transmit function is disabled.

This node is

not connected to the network.

In addition to the Diagnostic Status Register

bits, the COM90C66 contains two pins for direct

connection to LED's. These pins are meant to

immediately provide basic visual information on

board and network activity with decreased

dependence upon software.

The COM90C66

contains an internal retriggerable digital one-

shot which allows the nTXLED to light for 726

+/-10%

each

time

the

COM90C66 transmits information. Every time

the host accesses either the internal RAM,

registers, or external PROM, the nBSLED will

light for 400 mS +/- 20%. The sink capability of

both the nTXLED and nBSLED pins is 10mA,

thus allowing direct connection to the LED's to

be supported by

the

COM90C66. The only

additional components are 500

Ω resistors

between the LED's and VCC.

COM90C66 Datasheet(PDF) 44 Page - SMSC Corporation

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