RE: Clause 49 /A/ /K/ /R/ on XGMII question
Justin,
The XGXS only converts /A/, /K/, and /R/ to /I/ when they occur in a whole
column: an ||A||, ||K||, or ||R|| ordered set. Therefore, one type of error
that would cause /A/, /K/, or /R/ on the XGMII output from an XGXS would be
a bit error that changed the value of one or more bytes in an ordered set.
If such an error happens, there is no particular reason for a 10GBASE-R PCS
to change the remaining /A/, /K/ and /R/ symbols to an /E/. We have code
table entries for them and replacing them with something else would
complicate implementation.
The primary purposes of sending an /E/ are:
to avoid changing an unencodeable input into something that might produce
an undetectable error.
to propogate special error detection that preserves delimiter Hamming
distance so that code dependent 0- to 3-bit errors don't produce
undetectable errors.
Neither of those purposes would be served by changing a spurious /A/, /K/ or
/R/ into an /E/. Furthermore, the RS has to handle receiving these /A/, /K/
and /R/ code groups because an XGXS might be directly connected to the RS.
If one believes that /A/, /K/ and /R/ should not be allowed to exist at the
XGMII interface, than it is the 10GBASE-X/XGXS coding rules that should be
changed and not 10GBASE-R.
Regards,
Pat
-----Original Message-----
From: Justin Gaither [mailto:jgaither@xxxxxxxxxxxxxxx]
Sent: Wednesday, February 14, 2001 11:29 AM
To: 802.3ae
Subject: Clause 49 /A/ /K/ /R/ on XGMII question
Hello,
Page 345 line 30-31 says "The codes for /A/ /K/ and /R/ are used on
the
XAUI interface to signal idle. They are not present on the XGMII when
no errorrs have occurred, but certain bit errors cause the XGXS to send
them on the XGMII."
What types of errors would this be? and why would we want allow them to
continue through the 10GBase-R, into the optional WIS and onto the link?
Should these be replaced by /E/?
--
Justin Gaither Phone: 512-306-7292 x529
RocketChips a Division of Xilinx Fax: 512-306-7293
500 N. Capital of TX Hwy.
Bldg 3 email: jgaither@xxxxxxxxxxxxxxx
Austin, TX 78746 WWW: www.rocketchips.com