From: "Dan" Newsgroups: comp.arch.fpga Subject: DLLs driving DLLs in Virtex. Lines: 20 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Message-ID: <17OV5.34236$2A2.1571588@news20.bellglobal.com> Date: Fri, 01 Dec 2000 13:57:17 GMT NNTP-Posting-Host: 64.230.1.140 X-Trace: news20.bellglobal.com 975679037 64.230.1.140 (Fri, 01 Dec 2000 08:57:17 EST) NNTP-Posting-Date: Fri, 01 Dec 2000 08:57:17 EST Organization: Sympatico Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.nextra.ch!news1.sunrise.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!sunqbc.risq.qc.ca!news3.bellglobal.com!nf2.bellglobal.com!news20.bellglobal.com.POSTED!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:3060 Hello, Is is possible to drive the input of a DLL with the output of another DLL ? I need to multiply by 4. A DLL will only multiply by 2. Will the resultant 4X clock have poor characteristics if I do this? (unstability/ bad jitter/ loss of lock ......) ? Also, I may want to use tw DLL to get multiply by 1.3333 ( 1st DLL 2X, 2nd DLL /1.5) Sincerely Daniel DeConinck High Res Technologies, Inc. ###### From: "Keith R. Williams" Newsgroups: comp.arch.fpga Subject: Re: DLLs driving DLLs in Virtex. Date: Fri, 01 Dec 2000 10:08:19 -0500 Organization: IBM Global Services North -- Burlington, Vermont, USA Lines: 23 Message-ID: <3A27BEE3.A2176A7@btv.ibm.com> References: <17OV5.34236$2A2.1571588@news20.bellglobal.com> NNTP-Posting-Host: prowler.btv.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: news.btv.ibm.com 975683644 27970 9.66.117.18 (1 Dec 2000 15:14:04 GMT) X-Complaints-To: news@btv.ibm.com NNTP-Posting-Date: 1 Dec 2000 15:14:04 GMT X-Mailer: Mozilla 4.7 [en] (WinNT; U) X-Accept-Language: en Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!portc03.blue.aol.com!newsjunkie.ans.net!news.chips.ibm.com!newsfeed.btv.ibm.com!news.btv.ibm.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:3037 Dan wrote: > > Hello, > > Is is possible to drive the input of a DLL with the output of another DLL ? > > I need to multiply by 4. A DLL will only multiply by 2. > > Will the resultant 4X clock have poor characteristics if I do this? > (unstability/ bad jitter/ loss of lock ......) ? Yes. See Xilinx application note XAPP132 (page 12-13). > Also, I may want to use tw DLL to get multiply by 1.3333 ( 1st DLL 2X, 2nd > DLL /1.5) Dunno. Ths sounds iffy, though perhaps you might be able to multiply by 4 (see above) and divide by 3 in some fashion? ---- Keith ###### Message-ID: <3A27C2E5.405958CA@andraka.com> From: Ray Andraka Organization: Andraka Consulting Group, Inc X-Mailer: Mozilla 4.73 [en] (WinNT; I) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: DLLs driving DLLs in Virtex. References: <17OV5.34236$2A2.1571588@news20.bellglobal.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 27 Date: Fri, 01 Dec 2000 15:24:05 GMT NNTP-Posting-Host: 24.13.238.93 X-Complaints-To: abuse@home.net X-Trace: news1.wwck1.ri.home.com 975684245 24.13.238.93 (Fri, 01 Dec 2000 07:24:05 PST) NNTP-Posting-Date: Fri, 01 Dec 2000 07:24:05 PST Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newshub2.home.com!news.home.com!news1.wwck1.ri.home.com.POSTED!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:3044 See the app-notes on using DLLs. I think it is numbered up around #232. The 4x is described carefully in the Appnote and includes a VHDL example. Dan wrote: > > Hello, > > Is is possible to drive the input of a DLL with the output of another DLL ? > > I need to multiply by 4. A DLL will only multiply by 2. > > Will the resultant 4X clock have poor characteristics if I do this? > (unstability/ bad jitter/ loss of lock ......) ? > > Also, I may want to use tw DLL to get multiply by 1.3333 ( 1st DLL 2X, 2nd > DLL /1.5) > > Sincerely > Daniel DeConinck > High Res Technologies, Inc. -- -Ray Andraka, P.E. President, the Andraka Consulting Group, Inc. 401/884-7930 Fax 401/884-7950 email ray@andraka.com http://www.andraka.com or http://www.fpga-guru.com ###### From: Vikram Pasham Newsgroups: comp.arch.fpga Subject: Re: DLLs driving DLLs in Virtex. Date: Fri, 01 Dec 2000 20:35:48 -0800 Organization: Xilinx Lines: 86 Message-ID: <3A287C24.E89B89D3@xilinx.com> References: <17OV5.34236$2A2.1571588@news20.bellglobal.com> Reply-To: Vikram.Pasham@xilinx.com NNTP-Posting-Host: vikramp.xsj.xilinx.com Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------64DBD04C3BE1155F277E6C3D" X-Mailer: Mozilla 4.61 [en] (WinNT; U) X-Accept-Language: en To: Dan Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.direct.ca!look.ca!nntp2.aus1.giganews.com!NetNews1!attla1!attla2!ip.att.net!newsgate.xilinx.com!cliff.xsj.xilinx.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:3069 --------------64DBD04C3BE1155F277E6C3D Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Hello Dan, Its possible to connect two DLLs in series to generate a 4x clock. Each DLL has +/- 60ps jitter and this may be accumulated or compensated across both DLLs. Just make sure the external input clock doesn't have any jitter, as this would be propagated through the DLLs. Other than this, the 4x clock will be stable and does not loose lock unless one of the DLL is reset or the input clock frequency changes. You can refer XAPP132: Using the Virtex Delay-Locked Loop available at http://support.xilinx.com/apps/virtexapp.htm This app. note explains details on generating 4x clock with two DLLs and other DLL applications. Also refer Virtex datasheet for DLL specs. -Vikram Xilinx Applications Dan wrote: > Hello, > > Is is possible to drive the input of a DLL with the output of another DLL ? > > I need to multiply by 4. A DLL will only multiply by 2. > > Will the resultant 4X clock have poor characteristics if I do this? > (unstability/ bad jitter/ loss of lock ......) ? > > Also, I may want to use tw DLL to get multiply by 1.3333 ( 1st DLL 2X, 2nd > DLL /1.5) > > Sincerely > Daniel DeConinck > High Res Technologies, Inc. --------------64DBD04C3BE1155F277E6C3D Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Hello Dan,

Its possible to connect two DLLs in series to generate a 4x clock. Each DLL has +/- 60ps jitter and this may be accumulated or compensated across both DLLs. Just make sure the external input clock doesn't have any jitter, as this would be propagated through the DLLs. Other than this, the  4x clock will be stable and does not loose lock unless  one of the DLL is reset or the input clock frequency changes.

You can refer XAPP132: Using the Virtex Delay-Locked Loop available at
http://support.xilinx.com/apps/virtexapp.htm

This app. note explains details on generating 4x clock with two DLLs and other DLL applications. Also refer Virtex datasheet for DLL specs.

-Vikram
Xilinx Applications
 
 
 
 

Dan wrote:

Hello,

Is is possible to drive the input of a DLL with the output of another DLL ?

I need to multiply by 4. A DLL will only multiply by 2.

Will the resultant 4X clock have poor characteristics if I do this?
(unstability/ bad jitter/ loss of lock ......) ?

Also, I may want to use tw DLL to get multiply by 1.3333 ( 1st DLL 2X, 2nd
DLL /1.5)

Sincerely
Daniel DeConinck
High Res Technologies, Inc.

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