COM20020IP3V datasheet(35/82 Pages) SMSC

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Table 5 - Diagnostic Status Register

BIT

BIT NAME

SYMBOL

DESCRIPTION

Reconfiguration

MY-

RECON

This bit, if high, indicates that a past reconfiguration was caused by

this node.

It is set when the Lost Token Timer times out, and

should be typically read following an interrupt caused by RECON.

Refer to the Improved Diagnostics section for further detail.

Duplicate ID

DUPID

This bit, if high, indicates that the value in the Node ID Register

matches both Destination ID characters of the token and a

response to this token has occurred.

Trailing zero's are also

verified. A logic "1" on this bit indicates a duplicate Node ID, thus

the user should write a new value into the Node ID Register. This

bit is only useful for duplicate ID detection when the device is off

line, that is, when the transmitter is disabled. When the device is

on line this bit will be set every time the device gets the token. This

bit is reset automatically upon reading the Diagnostic Status

Refer to the Improved Diagnostics section for further

detail.

Receive

Activity

RCVACT

This bit, if high, indicates that data activity (logic "1") was detected

on the RXIN pin of the device. Refer to the Improved Diagnostics

section for further detail.

Token Seen

TOKEN

This bit, if high, indicates that a token has been seen on the

network, sent by a node other than this one. Refer to the Improved

Diagnostic section for further detail.

Excessive NAK

EXCNAK

This bit, if high, indicates that either 128 or 4 Negative

Acknowledgements have occurred in response to the Free Buffer

Enquiry. This bit is cleared upon the "POR Clear Flags" command.

Reading the Diagnostic Status Register does not clear this bit.

This bit, when set, will cause an interrupt if the corresponding bit in

the IMR is also set. Refer to the Improved Diagnostics section for

further detail.

Tentative ID

TENTID

This bit, if high, indicates that a response to a token whose DID

matches the value in the Tentative ID Register has occurred. The

second DID and the trailing zero's are not checked. Since each

node sees every token passed around the network, this feature

can be used with the device on-line in order to build and update a

network map. Refer to the Improved Diagnostics section for further

detail.

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