From: nagaraj_c_s@yahoo.com (Nagaraj) Newsgroups: comp.arch.fpga Subject: Crystal Input to FPGA Date: 10 Sep 2003 05:48:28 -0700 Organization: http://groups.google.com/ Lines: 10 Message-ID: <91710219.0309100448.6e8ab050@posting.google.com> NNTP-Posting-Host: 164.164.69.252 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1063198111 30383 127.0.0.1 (10 Sep 2003 12:48:31 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: 10 Sep 2003 12:48:31 GMT Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.imp.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.stanford.edu!postnews1.google.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32753 Hi, I want to interface a crystal to a Xilinx FPGA. Earlier Xilinx FPGA devices like XC2000 series had crystal input provision which is not there in Spartan 30K gate device which I am using for my design. I want to know how to build an oscillator circuit (amplifier) for the crystal in FPGA. Any references? Regards, Nagaraj ###### From: "Jonathan Bromley" Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Wed, 10 Sep 2003 14:16:48 +0100 Lines: 29 Message-ID: References: <91710219.0309100448.6e8ab050@posting.google.com> NNTP-Posting-Host: external-2.doulos.co.uk X-Trace: news.demon.co.uk 1063199975 25895 62.49.79.188 (10 Sep 2003 13:19:35 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Wed, 10 Sep 2003 13:19:35 +0000 (UTC) X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4910.0300 X-Priority: 3 X-Newsreader: Microsoft Outlook Express 5.50.4807.1700 X-MSMail-Priority: Normal Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!kibo.news.demon.net!news.demon.co.uk!demon!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32748 "Nagaraj" wrote in message news:91710219.0309100448.6e8ab050@posting.google.com... > I want to interface a crystal to a Xilinx FPGA. Earlier Xilinx FPGA > devices like XC2000 series had crystal input provision which is not > there in Spartan 30K gate device which I am using for my design. > I want to know how to build an oscillator circuit (amplifier) for > the crystal in FPGA. Don't mess around. Buy a packaged oscillator. The price of the oscillator is about three orders of magnitude lower than the value of the headaches you will get from not using one. -- Jonathan Bromley, Consultant DOULOS - Developing Design Know-how VHDL * Verilog * SystemC * Perl * Tcl/Tk * Verification * Project Services Doulos Ltd. Church Hatch, 22 Market Place, Ringwood, Hampshire, BH24 1AW, UK Tel: +44 (0)1425 471223 mail: jonathan.bromley@doulos.com Fax: +44 (0)1425 471573 Web: http://www.doulos.com The contents of this message may contain personal views which are not the views of Doulos Ltd., unless specifically stated. ###### From: Peter Alfke Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Wed, 10 Sep 2003 09:24:51 -0700 Organization: Xilinx,Inc Lines: 28 Message-ID: <3F5F5053.1FBF30EA@xilinx.com> References: <91710219.0309100448.6e8ab050@posting.google.com> NNTP-Posting-Host: peter.xilinx.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.77C-CCK-MCD {C-UDP; EBM-APPLE} (Macintosh; U; PPC) X-Accept-Language: en To: Nagaraj Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.imp.ch!news.imp.ch!zen.net.uk!in.100proofnews.com!in.100proofnews.com!attla2!attla1!ip.att.net!newsgate.xilinx.com!cliff.xsj.xilinx.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32737 Don't do it! In XC3000 we had a single-stage amplifier between two pins, and that worked kind of ok with most crystals. But there were problems with very low frequencies (like 32 kHz) and some overtone designs. We (i.e.I) got dragged into many complicated analog discussions, so we never offered such a circuit again. If you implement an inverter from one input pin to an output pin, you actually have more than half a dozen stages cascaded (that's the way we build our input and output buffers) and that is not a healthy arrangement for a reliable oscillator that always starts and never goes into spurious odcillations. It might work in the lab, but is not good for production. Buy a complete oscillator can. You can buy them retail for <$1, and they always work and draw little power. Peter Alfke, Xilinx Applications ==================== Nagaraj wrote: > > Hi, > I want to interface a crystal to a Xilinx FPGA. Earlier Xilinx FPGA > devices like XC2000 series had crystal input provision which is not > there in Spartan 30K gate device which I am using for my design. > I want to know how to build an oscillator circuit (amplifier) for > the crystal in FPGA. > Any references? > > Regards, > Nagaraj ###### From: panteltje@yahoo.com (Jan Panteltje) Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: 10 Sep 2003 16:16:33 -0700 Organization: http://groups.google.com/ Lines: 61 Message-ID: References: <91710219.0309100448.6e8ab050@posting.google.com> NNTP-Posting-Host: 195.240.108.48 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1063235794 3890 127.0.0.1 (10 Sep 2003 23:16:34 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: 10 Sep 2003 23:16:34 GMT Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!news.maxwell.syr.edu!newsfeed.stanford.edu!postnews1.google.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32803 nagaraj_c_s@yahoo.com (Nagaraj) wrote in message news:<91710219.0309100448.6e8ab050@posting.google.com>... > Hi, > I want to interface a crystal to a Xilinx FPGA. Earlier Xilinx FPGA > devices like XC2000 series had crystal input provision which is not > there in Spartan 30K gate device which I am using for my design. > I want to know how to build an oscillator circuit (amplifier) for > the crystal in FPGA. > Any references? > > Regards, > Nagaraj >Hi, > I want to interface a crystal to a Xilinx FPGA. Earlier Xilinx FPGA >devices like XC2000 series had crystal input provision which is not >there in Spartan 30K gate device which I am using for my design. > I want to know how to build an oscillator circuit (amplifier) for >the crystal in FPGA. > Any references? > >Regards, >Nagaraj > mmm many people are paranoid about xtal oscillators it seems. Still I agree the small integrated DIL ones are cheap and easy, but for the ones who MUST use an xtal when all shops are closed, this solution has always worked for me: +5V | drain |---- ----------------------->| BF245 B | | | |---- | | === C |-----------0 to TTL level input | | |-------------| | | | | --- | | | | | = | | | | | --- | |100k | | | 1k5 |XTAL | === 2 C | | | | | -----------------------------------------0 It can drive a HCT7404 or such directly. Stability is very very good. The caps ratio is 1 to 2 C, values like 22 and 44 pF (2 22 in parallel) I use. If the drawing looks distorted use a fixed spacing font perhaps. I have uses this at 20MHz, 8.8MHz, 6 MHz, 100kHz, etc... Always works. Decauple the +5. The output looks like a sine wave, bit flatted, but very clean. If you want total separation, you can use a drain resistor and take the signal from there. Add a varicap with a small series cap parallel to the XTAL to make a voltage controlled oscillator for a PLL etc.. (For example color subcarrier lock). JP ###### From: Peter Alfke Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Wed, 10 Sep 2003 16:59:32 -0700 Organization: Xilinx,Inc Lines: 45 Message-ID: <3F5FBAE4.7663DE48@xilinx.com> References: <91710219.0309100448.6e8ab050@posting.google.com> NNTP-Posting-Host: peter.xilinx.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.77C-CCK-MCD {C-UDP; EBM-APPLE} (Macintosh; U; PPC) X-Accept-Language: en To: Jan Panteltje Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!newsfeed.media.kyoto-u.ac.jp!Spring.edu.tw!news.nctu.edu.tw!feeder.seed.net.tw!attdv1!attdv2!ip.att.net!newsgate.xilinx.com!cliff.xsj.xilinx.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32776 This is a classical circuit that always works. Note that there is only a single stage of amplification, a single transistor. So no weird phase/gain characteristi, just a single stage with a 6dB per octave roll-off. Unfortunately you cannot implement this between two FPGA pins. We added too much stuff (for a good reason, to serve normal applications ). Peter Alfke ============ Jan Panteltje wrote: > > > mmm many people are paranoid about xtal oscillators it seems. > Still I agree the small integrated DIL ones are cheap and easy, > but for the ones who MUST use an xtal when all shops are closed, > this solution has always worked for me: > > +5V > | drain > |---- > ----------------------->| BF245 B > | | | |---- > | | === C |-----------0 to TTL level input > | | |-------------| > | | | | > --- | | | | | > = | | | | | > --- | |100k | | | 1k5 > |XTAL | === 2 C | > | | | | > -----------------------------------------0 > > It can drive a HCT7404 or such directly. > Stability is very very good. > The caps ratio is 1 to 2 C, values like 22 and 44 pF (2 22 in parallel) > I use. > > If the drawing looks distorted use a fixed spacing font perhaps. > I have uses this at 20MHz, 8.8MHz, 6 MHz, 100kHz, etc... > Always works. > Decauple the +5. > The output looks like a sine wave, bit flatted, but very clean. > If you want total separation, you can use a drain resistor and take > the signal from there. > Add a varicap with a small series cap parallel to the XTAL to make a voltage > controlled oscillator for a PLL etc.. > (For example color subcarrier lock). > JP ###### From: "Glen Herrmannsfeldt" Newsgroups: comp.arch.fpga References: <91710219.0309100448.6e8ab050@posting.google.com> Subject: Re: Crystal Input to FPGA Lines: 21 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.00.2919.6700 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 Message-ID: NNTP-Posting-Host: 12.207.204.17 X-Complaints-To: abuse@comcast.net X-Trace: sccrnsc02 1063242895 12.207.204.17 (Thu, 11 Sep 2003 01:14:55 GMT) NNTP-Posting-Date: Thu, 11 Sep 2003 01:14:55 GMT Organization: Comcast Online Date: Thu, 11 Sep 2003 01:14:55 GMT Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!news-out1.nntp.be!propagator2-sterling!In.nntp.be!newshosting.com!news-xfer1.atl.newshosting.com!diablo.voicenet.com!cycny01.gnilink.net!cyclone1.gnilink.net!wn14feed!wn13feed!worldnet.att.net!204.127.198.204!attbi_feed4!attbi.com!sccrnsc02.POSTED!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32779 "Nagaraj" wrote in message news:91710219.0309100448.6e8ab050@posting.google.com... > Hi, > I want to interface a crystal to a Xilinx FPGA. Earlier Xilinx FPGA > devices like XC2000 series had crystal input provision which is not > there in Spartan 30K gate device which I am using for my design. > I want to know how to build an oscillator circuit (amplifier) for > the crystal in FPGA. > Any references? The oscillator that I used to know used three CMOS inverting gates in series with the crystal wrapped around them. Possibly some resistors, too. Usually one more gate to buffer and shape the result. Though I remember people having a hard time sometimes with the 32kHz crystals, it worked well for everything else. -- glen ###### From: rickman Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Wed, 10 Sep 2003 22:06:21 -0400 Organization: Arius, Inc Lines: 35 Message-ID: <3F5FD89D.D7B92959@yahoo.com> References: <91710219.0309100448.6e8ab050@posting.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: UmFuZG9tSVamawD1NiqDwGnRu0LcsKidxMrmIVaYs13973XClh4tMg8/nFftBFyi X-Complaints-To: abuse@rcn.com NNTP-Posting-Date: 11 Sep 2003 02:06:16 GMT X-Mailer: Mozilla 4.73 [en] (Windows NT 5.0; U) X-Accept-Language: en Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!skynet.be!skynet.be!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!feed2.news.rcn.net!feed1.news.rcn.net!rcn!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32772 Glen Herrmannsfeldt wrote: > > "Nagaraj" wrote in message > news:91710219.0309100448.6e8ab050@posting.google.com... > > Hi, > > I want to interface a crystal to a Xilinx FPGA. Earlier Xilinx FPGA > > devices like XC2000 series had crystal input provision which is not > > there in Spartan 30K gate device which I am using for my design. > > I want to know how to build an oscillator circuit (amplifier) for > > the crystal in FPGA. > > Any references? > > The oscillator that I used to know used three CMOS inverting gates in series > with the crystal wrapped around them. Possibly some resistors, too. > Usually one more gate to buffer and shape the result. > > Though I remember people having a hard time sometimes with the 32kHz > crystals, it worked well for everything else. But what is the advantage over an oscillator unless you are trying to squeze every penny out of the design? The difference between an oscillator and a crystal is less than $.50. -- Rick "rickman" Collins rick.collins@XYarius.com Ignore the reply address. To email me use the above address with the XY removed. Arius - A Signal Processing Solutions Company Specializing in DSP and FPGA design URL http://www.arius.com 4 King Ave 301-682-7772 Voice Frederick, MD 21701-3110 301-682-7666 FAX ###### From: "Peter Seng" Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Thu, 11 Sep 2003 10:31:02 +0200 Organization: 1&1 Internet AG Lines: 181 Message-ID: References: <91710219.0309100448.6e8ab050@posting.google.com> NNTP-Posting-Host: p50914e76.dip0.t-ipconnect.de X-Trace: online.de 1063269206 25012 80.145.78.118 (11 Sep 2003 08:33:26 GMT) X-Complaints-To: abuse@einsundeins.com NNTP-Posting-Date: Thu, 11 Sep 2003 08:33:26 +0000 (UTC) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!irazu.switch.ch!switch.ch!news-fra1.dfn.de!npeer.de.kpn-eurorings.net!rz.uni-karlsruhe.de!feed.news.schlund.de!schlund.de!news.online.de!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32771 "Nagaraj" schrieb im Newsbeitrag news:91710219.0309100448.6e8ab050@posting.google.com... > Hi, > I want to interface a crystal to a Xilinx FPGA. Earlier Xilinx FPGA > devices like XC2000 series had crystal input provision which is not > there in Spartan 30K gate device which I am using for my design. > I want to know how to build an oscillator circuit (amplifier) for > the crystal in FPGA. > Any references? > > Regards, > Nagaraj We did it using a spare 74HC14 gate cause Xilinx does not recommend to make oscillators with FPGA´s or CPLD´s, it had to be cheap, had to work from a 3V3 supply and the gate was not occupied. See attached schematic. The "100GHz" value for the crystal says that it is not assembled - the board can work with a small clock crystal Q1 or a standard HV49U-S crystal Q2. Values might depend on crystal and gate type. with best regards, Peter Seng ############################# SENG digitale Systeme GmbH Im Bruckwasen 35 D 73037 Göppingen Germany tel +7161-75245 fax +7161-72965 eMail p.seng@seng.de net http://www.seng.de ############################# begin 666 Oscillator.gif M1TE&.#=A'@+\`?<``````/___P``````1@$`````````)04``("&D2PY!0`` M@(:1+(CH!@``````Y3B(=P``!P!@DP@``````&3H!@"(!@<`&.D&`)4KB'<@ M.8AW_____RCI!@! MXQWZ!('`&B3" ```````````````0! ZR,``D `@ (` M``#XZ 8`SKJD=WCS!@#(&JEW0.LC`-B3!P"HY@8`*#JR=RCT!@`K3M1WT#G2 M=_____\LZ08`T\VD=V#$I'>RQ*1W^.@&`"CI!@!%````<#F(=P``!P!X$P<` M10```- A!P``Z08```(``+SJ!@"5*XAWN#F(=______,Z@8`)[*,=W@3!P`* M`@``&@(```````!@*+)W:),(`$7-I'=HDP@`Q.HC`"CJ(P!05J=W/@````,# M````````P ```````$9$`#H`7 !4`$4`30!0`%P`3P!3`$,`20!,`$P`00!4 M`$\`4@`N`$<`20!&````!@#(Z08`U3C@=_5BB'<```,!4/,&`/5BB'<```,! 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`3_?]0VF5)S1 M-COHX[SAFY)R_'JWT2$:$(?WJYESQ8VA6 M[QT,DQ%MW$&/]0K?D;$*]T_;>[/I< MX'XZQQY/]^*-N57=]&XO\VO?%!5N1VZ_%E8OTX Newsgroups: comp.arch.fpga References: <91710219.0309100448.6e8ab050@posting.google.com> <3F5FD89D.D7B92959@yahoo.com> Subject: Re: Crystal Input to FPGA Lines: 25 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.00.2919.6700 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 Message-ID: NNTP-Posting-Host: 12.207.204.17 X-Complaints-To: abuse@comcast.net X-Trace: sccrnsc04 1063335195 12.207.204.17 (Fri, 12 Sep 2003 02:53:15 GMT) NNTP-Posting-Date: Fri, 12 Sep 2003 02:53:15 GMT Organization: Comcast Online Date: Fri, 12 Sep 2003 02:53:15 GMT Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!news-out1.nntp.be!propagator2-sterling!news-in-sterling.nuthinbutnews.com!cyclone1.gnilink.net!in.100proofnews.com!in.100proofnews.com!attla2!ip.att.net!attbi_feed3!attbi.com!sccrnsc04.POSTED!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32836 "rickman" wrote in message news:3F5FD89D.D7B92959@yahoo.com... > Glen Herrmannsfeldt wrote: > > (snip about a crystal oscillator for use with FPGA's) > > The oscillator that I used to know used three CMOS inverting gates in series > > with the crystal wrapped around them. Possibly some resistors, too. > > Usually one more gate to buffer and shape the result. > > > > Though I remember people having a hard time sometimes with the 32kHz > > crystals, it worked well for everything else. > > But what is the advantage over an oscillator unless you are trying to > squeze every penny out of the design? The difference between an > oscillator and a crystal is less than $.50. Some people just don't like them, but otherwise I agree. -- glen ###### From: rickman Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Fri, 12 Sep 2003 00:57:31 -0400 Organization: Arius, Inc Lines: 43 Message-ID: <3F61523B.7F2FD05@yahoo.com> References: <91710219.0309100448.6e8ab050@posting.google.com> <3F5FD89D.D7B92959@yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: UmFuZG9tSVb04VMaPpPSQralFvdeXuGxUCVCHq1P5wZsVHTG/pjWDIWOHqCjdmn8 X-Complaints-To: abuse@rcn.com NNTP-Posting-Date: 12 Sep 2003 04:57:33 GMT X-Mailer: Mozilla 4.73 [en] (Windows NT 5.0; U) X-Accept-Language: en Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!news-out1.nntp.be!propagator2-sterling!news-in-sterling.newsfeed.com!newsfeed.mathworks.com!wn13feed!worldnet.att.net!199.184.165.233!feed2.news.rcn.net!feed1.news.rcn.net!rcn!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32889 Glen Herrmannsfeldt wrote: > > "rickman" wrote in message > news:3F5FD89D.D7B92959@yahoo.com... > > Glen Herrmannsfeldt wrote: > > > > > (snip about a crystal oscillator for use with FPGA's) > > > > The oscillator that I used to know used three CMOS inverting gates in > series > > > with the crystal wrapped around them. Possibly some resistors, too. > > > Usually one more gate to buffer and shape the result. > > > > > > Though I remember people having a hard time sometimes with the 32kHz > > > crystals, it worked well for everything else. > > > > But what is the advantage over an oscillator unless you are trying to > > squeze every penny out of the design? The difference between an > > oscillator and a crystal is less than $.50. > > Some people just don't like them, but otherwise I agree. I wouldn't know what there is not to like. An oscillator unit is smaller, simpler and works better than a crystal circuit you can design in just a few hours without extensive testing. If the cost difference is not an issue (such as production volumes below 10,000) I can't see how it would pay to design your own oscillator. Even with higher volume production, I bet the lower failure rate would make a self design not worth the effort. -- Rick "rickman" Collins rick.collins@XYarius.com Ignore the reply address. To email me use the above address with the XY removed. Arius - A Signal Processing Solutions Company Specializing in DSP and FPGA design URL http://www.arius.com 4 King Ave 301-682-7772 Voice Frederick, MD 21701-3110 301-682-7666 FAX ###### From: Brian Drummond Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Fri, 12 Sep 2003 19:17:23 +0100 Lines: 25 Message-ID: References: <91710219.0309100448.6e8ab050@posting.google.com> <3F5FD89D.D7B92959@yahoo.com> NNTP-Posting-Host: shapes.demon.co.uk Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: news.demon.co.uk 1063390707 5034 158.152.228.158 (12 Sep 2003 18:18:27 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Fri, 12 Sep 2003 18:18:27 +0000 (UTC) X-Newsreader: Forte Agent 1.7/32.534 Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!newsfeed.stueberl.de!peernews!peer.cwci.net!kibo.news.demon.net!news.demon.co.uk!demon!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32887 On Wed, 10 Sep 2003 22:06:21 -0400, rickman wrote: >Glen Herrmannsfeldt wrote: >> The oscillator that I used to know used three CMOS inverting gates in series >> with the crystal wrapped around them. Possibly some resistors, too. >> Usually one more gate to buffer and shape the result. > >But what is the advantage over an oscillator unless you are trying to >squeze every penny out of the design? The difference between an >oscillator and a crystal is less than $.50. Off the shelf oscillators for standard frequencies are one thing. But when I was looking for custom frequencies I found manufacturers were happy to make small batch or even one-off crystals at a very respectable price; at the time, they didn't seem to be tooled up to make one-off oscillator modules - or at least they wanted much more money for the job. Maybe this has changed in the last few years. - Brian ###### From: hmurray@suespammers.org (Hal Murray) Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Sat, 13 Sep 2003 00:36:21 -0000 Message-ID: X-Newsreader: xrn 9.02 Sender: murray@glypnod (Hal Murray) References: <91710219.0309100448.6e8ab050@posting.google.com> <3F5FD89D.D7B92959@yahoo.com> X-Complaints-To: abuse@supernews.com Lines: 18 Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!feed.news.nacamar.de!news.maxwell.syr.edu!sn-xit-03!sn-xit-06!sn-post-02!sn-post-01!supernews.com!corp.supernews.com!glypnod!hmurray Xref: chonsp.franklin.ch comp.arch.fpga:32853 >But when I was looking for custom frequencies I found manufacturers were >happy to make small batch or even one-off crystals at a very respectable >price; at the time, they didn't seem to be tooled up to make one-off >oscillator modules - or at least they wanted much more money for the >job. Fox has custom frequency oscillators availably at reasonably cost and reasonably quickly. http://www.foxonline.com/jitomain.htm I expect there are others. -- The suespammers.org mail server is located in California. So are all my other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited commercial e-mail to my suespammers.org address or any of my other addresses. These are my opinions, not necessarily my employer's. I hate spam. ###### From: "Daniel Lang" Newsgroups: comp.arch.fpga Subject: Re: Crystal Input to FPGA Date: Fri, 12 Sep 2003 17:43:42 -0700 Organization: California Institute of Technology, Pasadena Lines: 18 Message-ID: References: <91710219.0309100448.6e8ab050@posting.google.com> <3F5FD89D.D7B92959@yahoo.com> NNTP-Posting-Host: dhcp-97-129.caltech.edu X-Trace: naig.caltech.edu 1063413825 3754 131.215.97.129 (13 Sep 2003 00:43:45 GMT) X-Complaints-To: abuse@caltech.edu NNTP-Posting-Date: Sat, 13 Sep 2003 00:43:45 +0000 (UTC) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Path: chonsp.franklin.ch!pfaff2.ethz.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!cyclone.bc.net!logbridge.uoregon.edu!nntp-server.caltech.edu!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:32841 "Brian Drummond" wrote in message > Off the shelf oscillators for standard frequencies are one thing. > > But when I was looking for custom frequencies I found manufacturers were > happy to make small batch or even one-off crystals at a very respectable > price; at the time, they didn't seem to be tooled up to make one-off > oscillator modules - or at least they wanted much more money for the > job. > > Maybe this has changed in the last few years Digi-Key carries several brands of off the shelf oscillators that they can program to your custom frequencies (qty = 1). Daniel Lang