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Message
From: "Kevin Kay" <Kevin.Kay@e...>
Date: Thu, 9 May 2002 14:02:18 -0400
Subject: RE: [ethmac] Cheap Ethernet PHY???
Kendin is now owned by Micrel. The KS8721 is a 2.5V part, you may need
an extra regulator depending upon your design (which may be fine if you
already require 2.5V on your board).
Altima (bought by Broadcom) also has some inexpensive PHYs in high
volume (e.g., AC101L). I don't know your voltage/power requirements,
but an inexpensive PHY is not so inexpensive if you have to add a
regulator to support its core voltage. The AC101L has a built in
regulator to generate the core voltage from 3.3V and is still
inexpensive (also available in industrial temp if needed). The mainline
Broadcom PHYs have more features (e.g., Auto-MDIX), but are more
expensive - thus the reason I suggested the Altima line for your
application. I don't know the details of your application, but be sure
you're not giving up a needed feature like Auto-MDIX, extended distance
support, etc., in exchange for a less expensive PHY.
I tried to find someone that just made a 10base PHY. I think
Micrel/Kendin makes one, but can't find it. Often everything is not on
the web site, though.
By a one-bit data bus, I assume the PHYs you have looked at have an SMII
or an SSMII interface on them. This is not really a problem, although
you will have to redo a the MAC code from opencores. The SMII interface
runs at 125MHz for both 10base and 100base speeds. I believe the SMII
packet is just repeated 10 times when you operate in 10base (I'm a
little rusty). The basic MII principles are the same. I would guess
you could just add an extra layer (essentially a serial to parallel
converter) to convert SMII into MII and use the core code. If you are
running in half duplex mode, you may have to do some math to make sure
the extra latency that you are introducing will not screw up collision
detection. If you are running point-to-point or full-duplex (don't know
your network topology), then collision detection does not matter, but
your MAC will not be truly generic and may only be able to support a
subset of the compliant topologies (which may or may not be OK for your
application).
Just some suggestions and thoughts.
Best of luck,
Kevin
-----Original Message-----
From: Tal Weiss [mailto:tal@c...]
Sent: Thursday, May 09, 2002 7:23 AM
To: ethmac@o...
Subject: RE: [ethmac] Cheap Ethernet PHY???
Try the Kendin KS8721 chip....
-----Original Message-----
From: Jeff Hanoch [mailto:jeff@l...]
Sent: Wednesday, May 08, 2002 4:03 PM
To: ethmac@o...
Subject: [ethmac] Cheap Ethernet PHY???
Hi all,
I am quite new to ethernet hardware. My next ASIC design may need to
support ethernet 10baseT, so I was looking at your Ethernet MAC. The
problem I am seeing is that the cheapest PHYs I am seeing have only 1
bit data busses. Being an ethernet newbie, I have not yet found out if
this is a problem. Will it work with your MAC which has 4 bit data
busses? The only PHYs I have seen that have 4 data bits are very
expensive. We do high volume consumer electronics, so I call anything
over $5 expensive. Intel has a part listed for $3.74/1K in Digi-Key.
But it has the 1 bit data pins.
If a 1 bit data bus will not work, does anyone know of an inexpensive
PHY that I may have missed which will work with your core?
Any advice would be appreciated.
Thanks,
Jeff
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