Re: [usb] A student need your help

[elite<liyicheng@yahoo.com>]

Vikas,thanks for help.
u mean the clock and the (bus) data rate are the same(480Mb/s),but I 
want to know how it is implement(for example ,in VHDL or verilog).
thanks!


----- Original Message ----- 
From: "Vikas T Rao " <vikasraot@m... > 
To: <usb@o... > 
Date: Wed, 19 Feb 2003 10:24:31 +0530 
Subject: Re: [usb] A student need your help 

> 
> 
> 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@y...  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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