Re: [usb] Endpoint Numbers

[Rudolf Usselmann <rudi@asics.ws>]

on 1/11/01 10:16, Peter Teng at peter_teng@el.nec.com 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

> 
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> 
> best regards,
> "Peter" Chu Tin Teng
> Computing technology I/O Group
> NEC Electronics Inc.
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