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embedded clock concept by Unknown on Sep 9, 2004			Not available!
Hi All, 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. Thanks, Enjoy Your Day Dipak Hi All, 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. Thanks, Enjoy Your Day Dipak

embedded clock concept by markus on Sep 9, 2004			markus Posts: 32 Joined: Dec 9, 2002 Last seen: Apr 30, 2013
From: Dipak Modi<<A HREF="http://www.opencores.org/mailman/listinfo/cores">dipakm at e...</A>> [q] 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. [/q] 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" From: Dipak Modidipakm at 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"

embedded clock concept by Unknown on Sep 9, 2004			Not available!
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 <A HREF="http://www.opencores.org/mailman/listinfo/cores">markus at reaaliaika.net</A> wrote: [q]From: Dipak Modi<<A HREF="http://www.opencores.org/mailman/listinfo/cores">dipakm at e...</A>> [q]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. [/q] 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" _______________________________________________ <A HREF="http://www.opencores.org/mailman/listinfo/cores">http://www.opencores.org/mailman/listinfo/cores</A> [/q] 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 at reaaliaika.net wrote: From: Dipak Modidipakm at 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" _______________________________________________ http://www.opencores.org/mailman/listinfo/cores

embedded clock concept by Unknown on Sep 9, 2004			Not available!
Dipak Modi wrote: [q] 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. [/q] Manchester codes are not the only possibility. Codes such as 8b10b are chosen with lower overhead than the 2x manchester requires to produce a transition-rich bitstream. And transitions are what you need to recover a clock. alternately the telecomms world scrambles data by xor-ing with a PRBS polynomial. Statistically this raises the transition density (for most data..) Overhead is less - and strings of more then 40 consecutive same bits are pretty rare. [q] Thanks OC group, Dipak <A HREF="http://www.opencores.org/mailman/listinfo/cores">markus at reaaliaika.net</A> wrote: [q] From: Dipak Modi<<A HREF="http://www.opencores.org/mailman/listinfo/cores">dipakm at e...</A>> [q] 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. [/q] 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" _______________________________________________ <A HREF="http://www.opencores.org/mailman/listinfo/cores">http://www.opencores.org/mailman/listinfo/cores</A> [/q] _______________________________________________ <A HREF="http://www.opencores.org/mailman/listinfo/cores">http://www.opencores.org/mailman/listinfo/cores</A>[/q] Dipak Modi wrote: 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. Manchester codes are not the only possibility. Codes such as 8b10b are chosen with lower overhead than the 2x manchester requires to produce a transition-rich bitstream. And transitions are what you need to recover a clock. alternately the telecomms world scrambles data by xor-ing with a PRBS polynomial. Statistically this raises the transition density (for most data..) Overhead is less - and strings of more then 40 consecutive same bits are pretty rare. Thanks OC group, Dipak markus at reaaliaika.net wrote: From: Dipak Modidipakm at 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" _______________________________________________ http://www.opencores.org/mailman/listinfo/cores _______________________________________________ http://www.opencores.org/mailman/listinfo/cores

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