OPENCORES.ORG

From: Dipak Modi<dipakm@e...>

Yes Markus,
Your answer is satisfactory. Now I can understand that if xfer is with 
NRZI then no matter of the data content the line regularly changes it's 
state and from this we can detect the xfer rate.

If xfer data stream is not NRZI then there must be either separate clock 
bus or 'PREAMBLE' pattern support. I would like to know about this 
PREAMBLE pattern technique for clock retrieval.

Thanks OC group,

Dipak

markus@r... wrote:

>From: Dipak Modi<dipakm@e...> 
>
>  
>
>>What is 'embedded clock' concept? I've heard that receiver device 
>>extracts clock from the data at its end. Any information given 
>>would be appreciated. 
>>    
>>
>
>Do you mean those serial protocols, where the encoding of the data 
>contains some means to synchronize the receiver to the data stream 
>(like USB's NRZI). The common thing is, that no matter of the data 
>content the line regularly changes it's state (using encoding or 
>synchronization patterns), so that you can synchronize the receiving to 
>the edges (and possibly detect the transfer speeds).
>
>This way you don't need additional clock line in the implementation, 
>while still getting somewhat reliable transfers.
>
>Google search: "return-to-zero" and "non-return to zero"
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>
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