RE: [ethmac] MAC frame memory

["Illan Glasner" <iglasner@zumanetworks.com>]

   Hi,

	Obviusly there are many reason to make all kind of sizes of fifo but assuming you don;t plan on having a full packet stored than 5 nibble is enough to compensate for the PPM and even this inculde large margin.

The PPM "effect" is about half nibble so if you start reading from the fifo when it have reach the middle you have 2 nibble margin in each side which is about 4 time the max requirment PPM.

Since 5 nibble are only 20 FF you can save a memorey and use it for other place where you might need large memorey or any other use you might have or maybe even be able to use smaller device.

have a nice day

   Illan


-----Original Message-----
From: Igor Mohor [mailto:igorm@opencores.org]
Sent: Monday, April 01, 2002 11:48 PM
To: ethmac@opencores.org
Subject: RE: [ethmac] MAC frame memory


You're wrong. There are two fifos in the MAC (for transmit and receive
frames).
At the moment each is 8 words big (will probably be changed to 16).
Transmit starts as soon as the tx fifo is full. As soon as there is space in
the fifo for additional word, it is filled up immediatelly.

When receiving frames: as soon as there is at least one word in the fifo
it's
transferred to the memory.

I'm changing the design right now to use bursts and to be able to use
non-alligned
memory to store/load data. It's finished but I have troubles with the
implementation.

Regards,
	Igor


> -----Original Message-----
> From: owner-ethmac@opencores.org [mailto:owner-ethmac@opencores.org]On
> Behalf Of wilton@mail.usa.com
> Sent: 29. marec 2002 12:56
> To: ethmac@opencores.org
> Subject: [ethmac] MAC frame memory
>
>
> Hi,
>
> I'm new in network and trying to understand this MAC controller. I was
> wondering why there is no memory to store the ethernet frame in the
> MAC controller. It seems to me that if the host want to send out a
> frame, it just transfer the frame to the controller 32 bits by 32
> bits. Am
> I right? If it is, how can the MAC controller ensure to transmit
> the whole
> frame continually if there is no frame memory in it?
>
> Any comments in this regard are highly appreciated.
>
> wilton
> --
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