COM20020 Datasheet, PDF (30/72 Pages) SMSC Corporation – COM20020 3.3V ULANC Universal Local Area Network Controller with 2K x 8 On-Board RAM

Table 5 - Diagnostic Status Register
BIT BIT NAME
7 My
Reconfiguration
6 Duplicate ID
5 Receive
Activity
4 Token Seen
3 Excessive NAK
2 Tentative ID
1 New Next ID
1,0 (Reserved)
SYMBOL
DESCRIPTION
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.
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
Register. Refer to the Improved Diagnostics section for further
detail.
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
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.
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.
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.
NEW
NXTID
This bit, if high, indicates that the Next ID Register has been
updated and that a node has either joined or left the network.
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. The bit is cleared by reading the Next ID Register.
These bits are undefined.
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