Filter
Top Products
40 Intel 8255x 10/100 Mbps Ethernet Controller Family Open Source Software Developer Manual
Host Software Interface
6.3.2.4 Statistical Counters
The 8255x provides information for network management by providing on-chip statistical counters
that track a variety of events associated with both transmit and receive. The counters are updated
by the device when it completes the processing of a frame. For example, after the completion of
transmitting a frame on the link or when receiving a frame, the counter is updated. The Statistical
Counters are reported to the software on demand by issuing the Dump Statistical Counters
command or the Dump and Reset Statistical Counters command in the SCB CUC field. The
counters are internal to the device and are listed in the table below.
Table 16. SCB General Pointer for the RU Command
RUC
Field
RU Command SCB General Pointer Added to
0NOP Don’t care
1 RU Start Pointer to first RFD in the Receive Frame Area RU Base
2 RU Resume Don’t care
3 Reserved Don’t care
4 RU Abort Don’t care
5 Load HDS Header Data Size (Upper 18 bits must be zero)
6 Load RU Base 32-bit Base Register for RU data structures
7 RBD Resume Don’t care
Table 17. Statistical Counters
Byte Offset Device Statistic
0
Transmit good frames. This counter contains the number of frames
transmitted properly on the link. It is updated only after the actual
transmission on the link is completed and not when the frame was read from
memory as is done for the TxCB status.
4
Transmit maximum collisions (MAXCOL) errors. This counter contains
the number of frames that were not transmitted because they encountered
the configured maximum number of collisions. This counter should only
increment when the network is heavily saturated with traffic.
8
Transmit late collisions (LATECOL) errors. This counter contains the
number of frames that were not transmitted since they encountered a
collision outside of the normal collision window.
12
Transmit underrun errors. This counter contains the number of frames
that were either not transmitted or retransmitted due to a transmit DMA
underrun. If the device is configured to retransmit on underrun, this counter
may be updated multiple times for a single frame. Underruns occur due to a
lack of PCI bandwidth resulting in the internal transmit FIFO running dry
during the transmission of a frame.
16
Transmit lost carrier sense (CRS). This counter contains the number of
frames transmitted by the device despite the fact that it detected the de-
assertion of CRS during the transmission.
20
Transmit deferred. This counter contains the number of frames that were
deferred before transmission due to activity on the link.
24
Transmit single collision. This counter contains the number of transmitted
frames that encountered only one collision.