ethernet phy or mac

Hi

Does anyone have any experiences with connecting a MAC rather than a
PHY to a spartan(3e).

I don't know yet whether to use a microblaze or my own state machine
to connect to the ethernet. For microblaze, xilinx cores seem to want
just an external PHY but surely a MAC would offload more stuff from
the FPGA.

Any thoughts appreciated.

Regards

Colin

colin wrote:

> Does anyone have any experiences with connecting a MAC rather than a
> PHY to a spartan(3e).

You probably need both.

The PHY is the magic interface to the wire.

The MAC is a digital interface that makes
it all look like registers to some cpu.
It might be on the PHY chip or it might
be a fpga module.

          -- Mike Treseler

Colin,

A MAC+PHY costs more then a PHY, but you save the MAC IP cost and
gates in the FPGA.  It is a good alternative to consider.

Xilinx has a MicroBlaze interface to this type of device, called the
EPC.  They also have an application note that describes how to use it:
   http://www.xilinx.com/bvdocs/appnotes/xapp924.pdf

The app note uses a piece of hardware that is no longer available
(Avnet P160 Comm 3 module), but you can look at the Spartan-3 Mini-
Module which also has the 91C111 MAC+PHY.

Bryan


colin wrote:
> Hi
>
> Does anyone have any experiences with connecting a MAC rather than a
> PHY to a spartan(3e).
>
> I don't know yet whether to use a microblaze or my own state machine
> to connect to the ethernet. For microblaze, xilinx cores seem to want
> just an external PHY but surely a MAC would offload more stuff from
> the FPGA.
>
> Any thoughts appreciated.
>
> Regards
>
> Colin

On 18 Oct, 15:50, Bryan <bryan.fletc...@avnet.com> wrote:
> Colin,
>
> A MAC+PHY costs more then a PHY, but you save the MAC IP cost and
> gates in the FPGA.  It is a good alternative to consider.
>
> Xilinx has a MicroBlaze interface to this type of device, called the
> EPC.  They also have an application note that describes how to use it:
>    http://www.xilinx.com/bvdocs/appnotes/xapp924.pdf
>
> The app note uses a piece of hardware that is no longer available
> (Avnet P160 Comm 3 module), but you can look at the Spartan-3 Mini-
> Module which also has the 91C111 MAC+PHY.
>
> Bryan
>
>
>
> colin wrote:
> > Hi
>
> > Does anyone have any experiences with connecting a MAC rather than a
> > PHY to a spartan(3e).
>
> > I don't know yet whether to use a microblaze or my own state machine
> > to connect to the ethernet. For microblaze, xilinx cores seem to want
> > just an external PHY but surely a MAC would offload more stuff from
> > the FPGA.
>
> > Any thoughts appreciated.
>
> > Regards
>
> > Colin- Hide quoted text -
>
> - Show quoted text -

Bryan

Thanks for your reply, as a result I've made a much better job of
searching the xilinx website.

Colin

Bryan <bryan.fletcher@avnet.com> writes:
> A MAC+PHY costs more then a PHY,

Although one would logically expect that to be the case, in my experience
it isn't always true.  I suspect it has to do with the high volume in
which PCI Ethernet MAC/PHY chips are used in PCs.

For instance, at one time a Realtek 10/100 MAC/PHY was quoted at a lower
price than the Realtek 10/100 standalone PHY, in the same quantity.  I don't
know if that's still the case.