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AR# 16698

LogiCORE Gigabit Ethernet MAC v3.0 - Behavior of half-duplex counters when the Gigabite Ethernet MAC core is in full-duplex mode


General Description: 

When I use the Gigabit Ethernet MAC core in full-duplex mode, the half-duplex counters still increment. Is this behavior correct?


Yes -- this behavior is correct. Even though these counters are incrementing, they should be treated as "don't cares" in the design when the core is used in full-duplex mode.  


When the half-duplex logic is committed from the core, the half-duplex-specific counters disappear. This results in the address decoding of the management interface becoming simplified due to an address-decoding wrap-around. Therefore, when the half-duplex logic is omitted, 0x40 is picking up the count from the counter at 0x0 (and, likewise, 0x44 from 0x04.)  


This is also true for the other half-duplex counters (e.g., 0x41 will mirror 0x01), but this is not noticed because these counters contain "0".

AR# 16698
Date Created 09/03/2007
Last Updated 05/15/2014
Status Archive
Type General Article