RE: [ethmac] RX MAC

["NewsGroup" <nbase@nbase.com>]

5-Oct-00

   Hi,

	Few comment for the MAC in
http://www.opencores.org/cores/ethmac/blocks_1/rxethmac/rxmodules.shtml


1.
using a SDF detector that get a signal from the RX Machine which make it
base on the rxdv is somewhat dangerus and wrong, you must take into
considuration the case that you will get ONLT SFD without preamble and than
the data.

now if you look on the rxdv in the state machine and clock after the raius
of rxdv you generate a signla to the sdf detector to start looking you
already MISSED this packet and lost it.

on the other hand if you make it combinatorial than why not siple pass the
rxdv directly to the SDF detector ?

2.
What is the purpose of the address match ?
unless you are intent to work as a switch and if so you need more than
single mac I see no reason for it as the switch that you are conneted to
will already make the learning and filtering .

3.
in the crc machine , you wrote "Computes a CRC across the data and compares
it with FCS field." I belive a easier way is simple to pass the crc field
through the crc machine and simple see that you get the "magic number".

Also why do you send th 9 MSB bit of the crc ?

4.
a small typo in the front page in
http://www.opencores.org/cores/ethmac/blocks_1/rxethmac/rxethmac.shtml where
it say
"Clock is provided by MII through rx_clk, which frequency is 25 MHz when
operates at 10 Mbps and 2.5 MHz when operates at 100 Mbps."
when of course the 25M is in 100Mb and 2.5 is in 10Mb.

have a nice day

   Illan