[usb] question about the DLL in the UTMI

[Jiang daosan <jiangdaosan@21cn.com>]

Hi,everyone:

    I have some questions about UTMI. Can someone help me?
Thank you.

  I saw a module with the name of "FS DLL & Data Recover"
in the figure2: UTM Function Block Diagram . I don't know 
the exact function of that module. The explanation in the 
UTMI Spec. is that:

5.2 HS DLL (High Speed Delay Line PLL)
The delay line PLL extracts clock and data from the data received 
over the USB 2.0 interface for reception by the Receive Deserializer. 
A vendor defined number of delayed clock taps are be used to sample the
received data. The data output from the DLL is synchronous with the local clock.

My question is :
How about the relation between the clock extracted from the the data received 
over the USB2.0 interface and the local clock ?  Why to exact clock from the 
received data?  Which clock is used to sample the recieved data, the exact clock or local
clock from the local Clock Multiplier ?
 What is the meaning of "Delay Line"? is it refer to the delayed clock taps of 
vendor defined ? I was so puzzled about DLL.

Thanks.
Best Regards.


*************************************************
Jiang daosan   jiangdaosan@21cn.com

Institute of RF&OE-IC of Soutneast University
http://iroi.seu.edu.cn/english/new/index.htm
Nanjing, China
*************************************************

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