From: "Dan" Newsgroups: comp.arch.fpga Subject: Can a fpga replace external inverters in a crystal osc ? Lines: 14 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Message-ID: Date: Sat, 21 Sep 2002 08:22:48 -0400 NNTP-Posting-Host: 64.229.161.165 X-Complaints-To: abuse@sympatico.ca X-Trace: news20.bellglobal.com 1032611058 64.229.161.165 (Sat, 21 Sep 2002 08:24:18 EDT) NNTP-Posting-Date: Sat, 21 Sep 2002 08:24:18 EDT Organization: Bell Sympatico Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!newsfeed1.cidera.com!Cidera!torn!nf1.bellglobal.com!nf2.bellglobal.com!news20.bellglobal.com.POSTED!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:21153 Hello, My design has a common low cost crystal oscillator. It uses two inverters HC7404 and a few caps & two res. Can the inverter chip be replace by the FPGA. Can I simply put the crystal across two IO pins ( I am using a Spartan IIE ) and configurae them as an inverter ( while keeping the caps and the res(s) ) ? Sincerely Dan ###### Message-ID: <3D8C886A.5EC5478C@andraka.com> From: Ray Andraka Organization: Andraka Consulting Group, Inc X-Mailer: Mozilla 4.77 [en] (WinNT; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 34 Date: Sat, 21 Sep 2002 14:50:26 GMT NNTP-Posting-Host: 68.15.41.165 X-Complaints-To: abuse@cox.net X-Trace: news1.east.cox.net 1032619826 68.15.41.165 (Sat, 21 Sep 2002 10:50:26 EDT) NNTP-Posting-Date: Sat, 21 Sep 2002 10:50:26 EDT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.mailgate.org!newsfeed.wirehub.nl!kibo.news.demon.net!demon!shale.ftech.net!news.ftech.net!peernews.cix.co.uk!newspeer1-gui.server.ntli.net!ntli.net!cox.net!p01!news1.east.cox.net.POSTED!53ab2750!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:21142 Not reliably. The HC7404 works because it is used as an amplifier, which can be done with a simple inverter. An FPGA has too many gain stages between the pins to be abused as an amplifier in an oscillator circuit. While it may work on the bench, it will not reliably start and maintain the fundamental frequency with variations in temp, process, and voltage. Why not use an integrated xtal oscillator instead of a simple crystal? The costs are nearly the same. Dan wrote: > Hello, > > My design has a common low cost crystal oscillator. It uses two inverters > HC7404 and a few caps & two res. > > Can the inverter chip be replace by the FPGA. Can I simply put the crystal > across two IO pins ( I am using a Spartan IIE ) and configurae them as an > inverter ( while keeping the caps and the res(s) ) ? > > Sincerely > Dan -- --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 "They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759 ###### Message-ID: <3D8CA1C6.ABD606CE@earthlink.net> From: Peter Alfke Reply-To: palfke@earthlink.net X-Mailer: Mozilla 4.61 (Macintosh; I; PPC) X-Accept-Language: en,de,pdf MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? References: <3D8C886A.5EC5478C@andraka.com> Content-Type: text/plain; charset=us-ascii; x-mac-type="54455854"; x-mac-creator="4D4F5353" Content-Transfer-Encoding: 7bit Lines: 18 Date: Sat, 21 Sep 2002 16:44:07 GMT NNTP-Posting-Host: 216.244.42.89 X-Complaints-To: abuse@earthlink.net X-Trace: newsread2.prod.itd.earthlink.net 1032626647 216.244.42.89 (Sat, 21 Sep 2002 09:44:07 PDT) NNTP-Posting-Date: Sat, 21 Sep 2002 09:44:07 PDT Organization: EarthLink Inc. -- http://www.EarthLink.net Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.imp.ch!news.imp.ch!newsfeed.stueberl.de!cox.net!newsfeed1.earthlink.net!newsfeed.earthlink.net!stamper.news.pas.earthlink.net!newsread2.prod.itd.earthlink.net.POSTED!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:21144 Ray Andraka wrote: > Not reliably. The HC7404 works because it is used as an amplifier, which can > be done with a simple inverter. An FPGA has too many gain stages between the > pins to be abused as an amplifier in an oscillator circuit. While it may work > on the bench, it will not reliably start and maintain the fundamental > frequency with variations in temp, process, and voltage. Why not use an > integrated xtal oscillator instead of a simple crystal? The costs are nearly > the same. Amen. Could not be said better... XC3000 has a dedicated single-stage amplifier between XTAL1 and XTAL2 pins. But no other FPGA family has repeated that dubious feature. Peter Alfke ###### Message-ID: <3D8D8D82.9CC39BC2@algor.co.uk> From: Rick Filipkiewicz X-Mailer: Mozilla 4.75 [en] (WinNT; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? References: <3D8C886A.5EC5478C@andraka.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Organization: MIPS Technologies (UK) Ltd Cache-Post-Path: mudchute.algor.co.uk!unknown@poplar.algor.co.uk X-Cache: nntpcache 2.4.0b2 (see http://www.nntpcache.org/) Lines: 23 Date: Sun, 22 Sep 2002 10:29:38 +0100 NNTP-Posting-Host: 62.254.210.129 X-Complaints-To: abuse@ntlworld.com X-Trace: newsfep2-win.server.ntli.net 1032686980 62.254.210.129 (Sun, 22 Sep 2002 10:29:40 BST) NNTP-Posting-Date: Sun, 22 Sep 2002 10:29:40 BST Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!proxad.net!proxad.net!newspeer1-gui.server.ntli.net!ntli.net!newsfep2-win.server.ntli.net.POSTED!53ab2750!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:21162 Ray Andraka wrote: > Not reliably. The HC7404 works because it is used as an amplifier, which can > be done with a simple inverter. An FPGA has too many gain stages between the > pins to be abused as an amplifier in an oscillator circuit. While it may work > on the bench, it will not reliably start and maintain the fundamental > frequency with variations in temp, process, and voltage. Why not use an > integrated xtal oscillator instead of a simple crystal? The costs are nearly > the same. > Do you happen to know if there's a 32.??Khz xtal osc. that uses sufficiently little power that it can run off a 3V coin cell ? or with some power-down mode ? The reason I ask is that I'd dearly like to replace the PIIX4 southbridge + CombiIO functions in an FPGA/CPLD and about the only thing that's hard is the real time clock. I've already got a CPLD on board so it could be replaced by a CoolRunner (II ?) to take the RTC function. Maybe this is just to perfectionist & I'll just bite the bullet and find a stand-alone PC-compatible RTC. ###### Message-ID: <3D8D91F1.7323@designtools.co.nz> From: Jim Granville Reply-To: jim.granville@designtools.co.nz Organization: Mandeno Granville elect X-Mailer: Mozilla 3.0C-XTRA (Win95; I) MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? References: <3D8C886A.5EC5478C@andraka.com> <3D8D8D82.9CC39BC2@algor.co.uk> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 45 Date: Sun, 22 Sep 2002 21:48:33 +1200 NNTP-Posting-Host: 203.79.104.99 X-Complaints-To: abuse@tsnz.net X-Trace: news02.tsnz.net 1032688251 203.79.104.99 (Sun, 22 Sep 2002 21:50:51 NZST) NNTP-Posting-Date: Sun, 22 Sep 2002 21:50:51 NZST Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!news-out.newsfeeds.com!propagator2-maxim!news-in.spamkiller.net!news02.tsnz.net!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:21165 Rick Filipkiewicz wrote: > > Ray Andraka wrote: > > > Not reliably. The HC7404 works because it is used as an amplifier, which can > > be done with a simple inverter. An FPGA has too many gain stages between the > > pins to be abused as an amplifier in an oscillator circuit. While it may work > > on the bench, it will not reliably start and maintain the fundamental > > frequency with variations in temp, process, and voltage. Why not use an > > integrated xtal oscillator instead of a simple crystal? The costs are nearly > > the same. > > > > Do you happen to know if there's a 32.??Khz xtal osc. that uses sufficiently > little power that it can run off a 3V coin cell ? or with some power-down mode ? > The reason I ask is that I'd dearly like to replace the PIIX4 southbridge + > CombiIO functions in an FPGA/CPLD and about the only thing that's hard is the real > time clock. I've already got a CPLD on board so it could be replaced by a > CoolRunner (II ?) to take the RTC function. > > Maybe this is just to perfectionist & I'll just bite the bullet and find a > stand-alone PC-compatible RTC. If you want to run of a coin cell, what's going to keep track of the time ? You could look at : Dallas DS32KHz - Not cheap, but high precision, and with battery pin. Intersil used to make a programmable OSC chip Or, make your own using HEF4069, or HEF4007 and a 32Khz xtal. Philips PCF8563 - docs suggest it defaults to 32KHz CLKOUT, so should power up without i2c BUS activity ? You could put a Read-Time state engine into the FPGA, and then the PCF8563.RTC can keep track of time, with << 1 uA Icc when in OFF mode. Seems the OSC is less of a problem, than the question of who's in charge of the time. -jg ###### Message-ID: <3D8DF15D.B9C2DD57@andraka.com> From: Ray Andraka Organization: Andraka Consulting Group, Inc X-Mailer: Mozilla 4.77 [en] (WinNT; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? References: <3D8C886A.5EC5478C@andraka.com> <3D8D8D82.9CC39BC2@algor.co.uk> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 37 Date: Sun, 22 Sep 2002 16:30:25 GMT NNTP-Posting-Host: 68.15.41.165 X-Complaints-To: abuse@cox.net X-Trace: news1.east.cox.net 1032712225 68.15.41.165 (Sun, 22 Sep 2002 12:30:25 EDT) NNTP-Posting-Date: Sun, 22 Sep 2002 12:30:25 EDT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!colt.net!easynet-quince!easynet.net!cox.net!p01!news1.east.cox.net.POSTED!53ab2750!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:21164 I believe Maxim and Dallas Semi both have something that will work for this. Rick Filipkiewicz wrote: > Ray Andraka wrote: > > > Not reliably. The HC7404 works because it is used as an amplifier, which can > > be done with a simple inverter. An FPGA has too many gain stages between the > > pins to be abused as an amplifier in an oscillator circuit. While it may work > > on the bench, it will not reliably start and maintain the fundamental > > frequency with variations in temp, process, and voltage. Why not use an > > integrated xtal oscillator instead of a simple crystal? The costs are nearly > > the same. > > > > Do you happen to know if there's a 32.??Khz xtal osc. that uses sufficiently > little power that it can run off a 3V coin cell ? or with some power-down mode ? > The reason I ask is that I'd dearly like to replace the PIIX4 southbridge + > CombiIO functions in an FPGA/CPLD and about the only thing that's hard is the real > time clock. I've already got a CPLD on board so it could be replaced by a > CoolRunner (II ?) to take the RTC function. > > Maybe this is just to perfectionist & I'll just bite the bullet and find a > stand-alone PC-compatible RTC. -- --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 "They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759 ###### From: kayrock66@yahoo.com (Jay) Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? Date: 22 Sep 2002 19:36:45 -0700 Organization: http://groups.google.com/ Lines: 39 Message-ID: References: <3D8C886A.5EC5478C@andraka.com> NNTP-Posting-Host: 66.81.19.230 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1032748606 7690 127.0.0.1 (23 Sep 2002 02:36:46 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: 23 Sep 2002 02:36:46 GMT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.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:21201 The costs are the same? Au contrair mon friar. According to my price book the crystal by itself is about 50 cents and the full up oscillator is $1.50, thats a dollar difference. So if is a low quantity, $1000 Vertex kinda thing, buy the can, but its high volume and real price sensitive, engineer and test your own. Ray Andraka wrote in message news:<3D8C886A.5EC5478C@andraka.com>... > Not reliably. The HC7404 works because it is used as an amplifier, which can > be done with a simple inverter. An FPGA has too many gain stages between the > pins to be abused as an amplifier in an oscillator circuit. While it may work > on the bench, it will not reliably start and maintain the fundamental > frequency with variations in temp, process, and voltage. Why not use an > integrated xtal oscillator instead of a simple crystal? The costs are nearly > the same. > > Dan wrote: > > > Hello, > > > > My design has a common low cost crystal oscillator. It uses two inverters > > HC7404 and a few caps & two res. > > > > Can the inverter chip be replace by the FPGA. Can I simply put the crystal > > across two IO pins ( I am using a Spartan IIE ) and configurae them as an > > inverter ( while keeping the caps and the res(s) ) ? > > > > Sincerely > > Dan > > -- > --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 > > "They that give up essential liberty to obtain a little > temporary safety deserve neither liberty nor safety." > -Benjamin Franklin, 1759 ###### From: hmurray@suespammers.org (Hal Murray) Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? Date: Wed, 25 Sep 2002 07:26:10 -0000 Message-ID: X-Newsreader: xrn 9.02 Sender: murray@glypnod (Hal Murray) References: <3D8C886A.5EC5478C@andraka.com> <3D8D8D82.9CC39BC2@algor.co.uk> X-Complaints-To: abuse@supernews.com Lines: 16 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!proxad.net!freenix!sn-xit-05!sn-xit-06!sn-post-02!sn-post-01!supernews.com!corp.supernews.com!glypnod!hmurray Xref: chonsp.franklin.ch comp.arch.fpga:21283 >Do you happen to know if there's a 32.??Khz xtal osc. that uses sufficiently >little power that it can run off a 3V coin cell ? or with some power-down mode ? >The reason I ask is that I'd dearly like to replace the PIIX4 southbridge + >CombiIO functions in an FPGA/CPLD and about the only thing that's hard is the real Look at Dallas/Maxim. Probably others too. (Maxim bought Dallas) In the old days, the RTC was a separate chip. Dallas was one of the main suppliers. They still make them. -- 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. ###### Message-ID: <3D930DF7.29A4D17E@andraka.com> From: Ray Andraka Organization: Andraka Consulting Group, Inc X-Mailer: Mozilla 4.77 [en] (WinNT; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? References: <3D8C886A.5EC5478C@andraka.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 48 Date: Thu, 26 Sep 2002 13:33:38 GMT NNTP-Posting-Host: 68.15.41.165 X-Complaints-To: abuse@cox.net X-Trace: news1.east.cox.net 1033047218 68.15.41.165 (Thu, 26 Sep 2002 09:33:38 EDT) NNTP-Posting-Date: Thu, 26 Sep 2002 09:33:38 EDT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.imp.ch!news.imp.ch!newsfeed.stueberl.de!cox.net!p01!news1.east.cox.net.POSTED!53ab2750!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:21339 When you consider all of the costs ( the extra parts -the passives and the HC04, extra board space, inventory costs, pick and place cost, increased failure rate costs, etc) the price does get closer to parity. Engineering involves tradeoffs of course, but that is not done properly unless all the costs and potential problems are considered. Using the FPGA for the inverting gain in an oscillator is not good practice because of the sensitivity to circuit parameters that you can't control. Jay wrote: > The costs are the same? Au contrair mon friar. According to my price > book the crystal by itself is about 50 cents and the full up > oscillator is $1.50, thats a dollar difference. So if is a low > quantity, $1000 Vertex kinda thing, buy the can, but its high volume > and real price sensitive, engineer and test your own. > > Ray Andraka wrote in message news:<3D8C886A.5EC5478C@andraka.com>... > > Not reliably. The HC7404 works because it is used as an amplifier, which can > > be done with a simple inverter. An FPGA has too many gain stages between the > > pins to be abused as an amplifier in an oscillator circuit. While it may work > > on the bench, it will not reliably start and maintain the fundamental > > frequency with variations in temp, process, and voltage. Why not use an > > integrated xtal oscillator instead of a simple crystal? The costs are nearly > > the same. > > > > > > -- > > --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 > > > > "They that give up essential liberty to obtain a little > > temporary safety deserve neither liberty nor safety." > > -Benjamin Franklin, 1759 -- --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 "They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759 ###### From: Austin Lesea Newsgroups: comp.arch.fpga Subject: Re: Can a fpga replace external inverters in a crystal osc ? Date: Thu, 26 Sep 2002 07:51:08 -0700 Organization: Xilinx Lines: 61 Message-ID: <3D931EDC.990D6689@xilinx.com> References: <3D8C886A.5EC5478C@andraka.com> <3D930DF7.29A4D17E@andraka.com> NNTP-Posting-Host: 149.199.54.117 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.79 [en]C-CCK-MCD (WinNT; U) X-Accept-Language: en,pdf Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.imp.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!logbridge.uoregon.edu!arclight.uoregon.edu!enews.sgi.com!nntp.wetware.com!attdv1!attdv2!ip.att.net!newsgate.xilinx.com!cliff.xsj.xilinx.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:21327 Ray, I agree. Using an FPGA IOB as an amplifier is something you can make work one time, maybe dozens of times, but with changes in process the parameters can change, and the oscillator may sometimes not start up. The Gain and Phase (and delay) of an IOB ->LUT->IOB is pretty hard to characterize! Fairchild actually has a series of CMOS logic that consists of logic elements in tiny packages (for those pesky need an inverter problems in a cell phones). Austin Ray Andraka wrote: > When you consider all of the costs ( the extra parts -the passives and the HC04, extra > board space, inventory costs, pick and place cost, increased failure rate costs, etc) the > price does get closer to parity. Engineering involves tradeoffs of course, but that is > not done properly unless all the costs and potential problems are considered. Using the > FPGA for the inverting gain in an oscillator is not good practice because of the > sensitivity to circuit parameters that you can't control. > > Jay wrote: > > > The costs are the same? Au contrair mon friar. According to my price > > book the crystal by itself is about 50 cents and the full up > > oscillator is $1.50, thats a dollar difference. So if is a low > > quantity, $1000 Vertex kinda thing, buy the can, but its high volume > > and real price sensitive, engineer and test your own. > > > > Ray Andraka wrote in message news:<3D8C886A.5EC5478C@andraka.com>... > > > Not reliably. The HC7404 works because it is used as an amplifier, which can > > > be done with a simple inverter. An FPGA has too many gain stages between the > > > pins to be abused as an amplifier in an oscillator circuit. While it may work > > > on the bench, it will not reliably start and maintain the fundamental > > > frequency with variations in temp, process, and voltage. Why not use an > > > integrated xtal oscillator instead of a simple crystal? The costs are nearly > > > the same. > > > > > > > > > -- > > > --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 > > > > > > "They that give up essential liberty to obtain a little > > > temporary safety deserve neither liberty nor safety." > > > -Benjamin Franklin, 1759 > > -- > --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 > > "They that give up essential liberty to obtain a little > temporary safety deserve neither liberty nor safety." > -Benjamin Franklin, 1759