4.0 Register Set
(Continued)
65
www.national.com
DP83816
4.2.24 Management Information Base Registers
The counters provide a set of statistics compliant with the
following management specifications: MIB II, Ether-like
MIB, and IEEE MIB. The values provided are accessed
through the various registers as shown below. All MIB
counters are cleared to 0 when read.
Due to cost and space limitations, the counter bit widths
provided in the DP83816 MIB are less than the bit widths
called for in the above specifications. It is assumed that
management agent software will maintain a set of fully
compliant statistic values ("software" counters), utilizing the
hardware counters to reduce the frequency at which these
"software" counters must be updated. Sizes for specific
hardware statistic counters were chosen such that the
count values will not roll over in less than 15 ms if
incremented at the theoretical maximum rates described in
the above specifications. However, given that the
theoretical maximum counter rates do not represent
realistic network traffic and events, the actual rollover rates
for the hardware counters are more likely to be on the
order of several seconds. The hardware counters are
updated automatically by the MAC on the occurrence of
each event.
Table 4-3 MIB Registers
Offset
Tag
Size
warning
(MS bits)
Description
0060h
RXErroredPkts
16
8
Packets received with errors. This counter is incremented for each
packet received with errors. This count includes packets which are
automatically rejected from the FIFO due to both wire errors and
FIFO overruns.
0064h
RXFCSErrors
8
4
Packets received with frame check sequence errors. This counter is
incremented for each packet received with a Frame Check
Sequence error (bad CRC).
Note:
For the MII interface, an FCS error is defined as a resulting
invalid CRC after CRS goes invalid and an even number of bytes
have been received.
0068h
RXMsdPktErrors
8
4
Packets missed due to FIFO overruns. This counter is incremented
for each receive aborted due to data or status FIFO overruns
(insufficient buffer space).
006Ch
RXFAErrors
8
4
Packets received with frame alignment errors. This counter is
incremented for each packet received with a Frame Check
Sequence error (bad CRC).
Note:
For the MII interface, an FAE error is defined as a resulting
invalid CRC on the last full octet, and an odd number of nibbles have
been received (Dribble nibble condition with a bad CRC).
0070h
RXSymbolErrors
8
4
Packets received with one or more symbol errors. This counter is
incremented for each packet received with one or more symbol
errors detected.
Note:
For the MII interface, a symbol error is indicated by the RXER
signal becoming active for one or more clocks while the RXDV signal
is active (during valid data reception).
0074h
RXFrameTooLong
4
2
Packets received with length greater than 1518 bytes (too long
packets). This counter is incremented for each packet received with
greater than the 802.3 standard maximum length of 1518 bytes.
0078h
TXSQEErrors
4
2
Loss of collision heartbeat during transmission. This counter is
incremented when the collision heartbeat pulse is not detected by
the PMD after a transmission.
Summary of Contents for DP83816AVNG
Page 106: ...105 www national com DP83816 Notes...
