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Message
From: Rudolf Usselmann <rudi@a...>
Date: Thu, 11 Jan 2001 12:16:23 +0700
Subject: Re: [usb] Endpoint Numbers
on 1/11/01 10:16, Peter Teng at peter_teng@e... wrote:
> Rudolf,
>
> Rudolf> OK, so you are saying that a given endpoint can only be on of the
> three (control, IN or OUT) ? I must have misunderstood the spec !
> Peter: Whatever you are doing now in bit 24-27 of endpoint CSR 4.4.1 of spec
> 0.4 is fine.
>
> Rudolf> So do you think I should make the actual endpoint ID (4 bit field)
> programmable ? At synthesis time somebody may instantiated 4 endpoints,
> but he want's them to be endpoint 0,1,5 and 6. Making it programmable the
> function software may choose the final endpoint numbers. If not they
> would be fixed 0,1,2,3 for the above example.
> Peter: There is no need for endpoint number field for endpoint CSR. Whatever
> endpoint not implemented can be read as all zero in endpoint CSR. They can
> either be synthesis out by script during compile time, or programmed during
> run time. In anyway, the register addressing depicts the endpoint number.
I think you misunderstood me. Let me try to explain this again:
The endpoint field in the CSR, is the actual endpoint number that is matched
against the endpoint number in a token from the host. Basically this would
provide a mechanism for changing the endpoint number if desired. I'm not
sure if that is necessary or useful.
Regarding the "S" bit: I have removed it completely. The functionality I was
proposing, would increase the latency of the core when responding with data
or receiving data. It would basically bring it to a crawl when a slow CPU is
used ...
I have now also added 4 buffer pointers and also size registers for each
buffer, so I know how much data to transmit or I will set the size to
indicate how much data I have received.
Do you have any other suggestions as to how I can enhance the core/make it
more useful ?
Thanks !
rudi
>
> If you don't see my response within 24 business hours to your email, please
> email me using pteng@m..., pteng@y... or peter_teng@e..., or
> please call me direct. Sorry in advance for the trouble that may caused you.
>
> best regards,
> "Peter" Chu Tin Teng
> Computing technology I/O Group
> NEC Electronics Inc.
> Physical address
> 3301 Olcott St.,
> Santa Clara, CA 95054
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