[ethmac] ethmac dma

[Damjan Lampret <damjanlampret@yahoo.com>]

Hello,

I am sending you an interface that I wrote for a commercial Ethernet
MAC core. This interface is basically DMA engine that sits between host
bus and actual ethernet MAC. It wasn't tested yet so be careful reading
the RTL (I'll post bugless version in a week).

TX goes like this: DMA fetches first 32-bit word from memory (via Dma*
bus interface and obviously this interface's local registers must first
be initialized through Opb* bus interface). Once first word is fetched,
lower byte is moved to serial buffer and transmit packet start frame
signal is asserted for one tx_clk. Bytes are moved to ethmac on every
tx_clk. When last byte is moved in, transmit packet end frame is
asserted for one tx_clk.

RX goes the same except ETHMAC signals start and end of frame. Frame is
obviously moved to memory though DMA.

regards,
Damjan


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