[realtek] Tx Status Questions (for RTL8139C)

Donald Becker becker@scyld.com
Thu Apr 18 13:22:02 2002

On Thu, 18 Apr 2002, Miao Qingjun wrote:
> What are the actual meanings of bits <Carrier Sense
> Lost> and <CD heart beat> of Tx Status of Tx Desc???
> And why they are set when Tx OK bit is set???

They make sense if you understand the physical layer signaling of
100baseTx, and how it evolved from coax-based Ethernet with external
tranceivers that provided "heartbeat" with a few invalid Rx bits at the
end of each transmit attempt.

Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993