RE: Clause 46 question
I'm surprised at the confusion, it was clear to me when I wrote it ;-)
The answer is 128 columns. Rate and frequency are not necessarily the same
thing and in many other areas of 802.3 we use rate without implying
frequency. To me, incrementing at RX_CLK rate implies counting on each
active edge of RX_CLK, not at the frequency of the clock signal. Please
submit a comment suggest improved text for the increment of col_cnt.
--Bob Grow
-----Original Message-----
From: Eric Lynskey [mailto:elynskey@xxxxxxxxxxx]
Sent: Wednesday, February 14, 2001 9:59 AM
To: stds-802-3-hssg@xxxxxxxx
Subject: Clause 46 question
Anyone,
Is the text in clause 46 correct when it says that 128 columns not
containing a Sequence ordered_set must be received to clear the link_fault
variable? The state machine needs the col_cnt variable to increment to 128,
and this increments at RX_CLK rate. My confusion is that RX_CLK is defined
as nominally 156.25 MHz. However, RXD<31:0> is sampled on both the rising
and falling edges of RX_CLK. This means that after 128 cycles of RX_CLK,
256 columns have been received. So, the real question is does the RS need
to see 4 Sequence ordered_sets in 128 columns or 256 columns? I believe
there may be some issues if the RS needs to see 4 ordered_sets in 128
columns when connected to an XGXS and XAUI on both ends. Before I look into
this more deeply, I'd like to know whether it's supposed to be 128 or 256
columns.
Eric Lynskey
UNH InterOperability Lab