Ethernet Chip Suggestion

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    I'm doing some research on network. I wanna a chip that can capture
runt frame in 2 bytes. Is there any suggestion?

Re: Ethernet Chip Suggestion

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As in, a runt frame that is 2 bytes long?  Or, did you mean something else?

The controllers I've looked at support turning off the MAC-layer
error-checking, so you should be able to receive clobbered packets in
the buffer.  How short, I can't say, as this is a really niche need.

I'd say, you'll need to read some datasheets, find some that look
promising, and test them.  Sounds like a lot of time & effort.

If it's not worth that much trouble, talk to Network General (Sniffer
manufacturer) and see what they have to say about your needs.  They're
most likely to know of a device / card / setup that could do this, but
it'll likely cost a lot.


Re: Ethernet Chip Suggestion
      It would cost too much time, so i came here to find someone have
ever done this before.
BTW: Most of datasheets do not provide the minimum frame length limited.

Re: Ethernet Chip Suggestion
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I know the ASIX AX88796L has a setting that allows you to read from the
FIFO queue (4 bytes long, I think) that's in front of the packet buffer.
  And, it offers an option to disable CRC checking and IIRC accept
errored packets.  Access to the FIFO queue would seem to be as close to
the wire as you can get with a normal Ethernet controller, so perhaps
it's capable.  (You can get test boards at )

It's a rare niche of folks who would test for this knowledge - primarily
packet capture / protocol analysis creators.  Patrick seems to be one
such person.  Others may be found on the Sourceforge Ethereal project,
at Network General, or at Wild Packets.

May I ask, what is your project that you need to salvage such small bits
of damaged packets?

Have you considered FPGA or DSP decoding of the front-end signal, as
someone else has suggested?


Re: Ethernet Chip Suggestion
        I am doing some research on network collisions that would need
a small runt capture. I think it is the best way to achieve the goal
with mature chips. FPGA and DSP may cost too much time. at the same
time, AX88796L's datasheet does not show the limit, that plus much risk
on our work:(.
       Thank you!

Re: Ethernet Chip Suggestion
Most Ethernet controller can receive small packets. But you may have to
write our own mac lever driver for the chip can configure it to do that. The
small frames may come back with error bits set in the status, which are
ignored since you wrote the driver.

Btw, I was a past Network General driver engineer, but that was many years
ago and the company has been sold/merged with MacAfee in 1998 and that spun
off again recently in 2004

Good luck, not for the faint at heart for those who haven't ever wrote
hardware drivers before.


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