Re: [usb] A student need your help

["Vikas T Rao " <vikasraot@myw.ltindia.com>]

hi,

1. the clock u should be using for doing protocol operations(like CRC,
bit stuffing, NRZI, serial to parallel & vice-versa) should be 480MHz.
the clock for internal parallel operations(like keeping data into FIFO,
processing of that data, etc) can be of you choice. if u have to do 16
bit parallel operations, then u should have 30MHz clock (30MHz X 16 =
480MHz). if 8 bit, then 60MHz has to be used. depending on the clock
being used for parallel operation, u can select the same crystal
frequency(i.e., either 30 or 60MHz).

2. buffer size = max.packet size + 2 CRC bytes. if incoming data is
more than the max. packet size + 2, then ur logic should be capable to
discard those extra bytes(as u can't spare other buffer locations with
these extra bytes) and report error.

hope ur doubts got cleared.

...Vikas Chandra Rao.

>>> liyicheng@yahoo.com 02/19/03 11:36AM >>>
Hi
I'm a student ,I must implement a usb2.0 core in my degree paper.And
I have some questions about it:
1. How determin the clock in usb bus (HS mode)
2.How calculate the buffer size in an isochronous endpoint(HS mode).

Thanks
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