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AR# 23305

Embedded Tri-mode Ethernet MAC Wrapper v4.1- Incorrect GT11 attributes


Strictly speaking, there is an incorrect attribute used with the Virtex-4 RocketIO. This might cause confusion, though it will not actually affect operation or interoperability. 


A comma in 1000BASE-X is a 7 bit sequence: there is a +ve and -ve version of this (0011111 or 1100000 - see IEEE802.3 clause 


In 1000BASE-X, the only code groups which are used and contain a comma are the +ve and -ve version of the /K28.5/ character (1100000101 or 0011111010).


Currently, the COMMA_10B_MASK value is set to 0x3FF. This considers all 10-bits ot the /K28.5/ to be a comma. Strictly speaking, a comma should only be identified by only 7 of these 10 bits and so we should set the COMMA_10B_MASK value to 0x07F. 


This is not really a problem because, as stated above, only /K28.5/ is used in 1000BASE-X mode. In other standards, /K28.1/ and /K28.7/ will also contain a comma. But these should never be received (unless caused by bit errors). So effectively the 10-bit comma detection is valid.

AR# 23305
Date Created 09/04/2007
Last Updated 05/20/2014
Status Archive
Type General Article