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Re: XGMII or SPI-4 ?

Wang Wendeh wrote:

> Hi Ben,
> Thank you for the valuable information. You mentioned that SPI-4 is an
> interface
> above MAC layer, so that means the MAC will be needed to be implemented in
> the PHY device, right? It is kind of different than before. I don't know if
> it will make
> the PHY device to be too complicated.

This is not entirely correct. The SPI-4 bus is used for layer 3 traffic.
In other word, the data on SPI-4 is TCP/IP packets. In order to get
to a PHY which is a layer 1 device, you need to go through a layer
2 device.

The purpose of this study group is to define layer 1 and layer 2
functional standards for systems implementing ethernet (layer 2)

It is anticipated that component vendors will develop PHY devices
with either a XAUI or XSBI (or potentially XGMII) bus interface
to a layer 2 MAC device. The system interface from the MAC
(which is beyond the scope of this study group) shall be a layer 3
type bus such as SPI-4.

Tim Warland     P.Eng.
Hardware Design Engineer  Broadband Products
High Performance Optical Component Solutions
Nortel Networks                (613)765-6634