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AR# 23138

LogiCORE Ethernet 1000BASE-X PCS/PMA or SGMII v7.0 Core - Comma mask attribute used for Virtex-4 Rocket IO incorrect


Strictly speaking, there is an incorrect attribute used with the Virtex-4 RocketIO. Although this incorrect attribute setting can cause confusion, it will not actually effect operation. 


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 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.


This attribute will be updated in 8.2i IP_Update 1.

AR# 23138
Date Created 09/04/2007
Last Updated 05/20/2014
Status Archive
Type General Article