Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > sci.electronics.design > #458064
| From | rickman <gnuarm@gmail.com> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: Binary counter - please check my work |
| Date | 2017-04-29 23:43 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <oe3mbm$3pt$1@dont-email.me> (permalink) |
| References | (3 earlier) <oe0vro$ogs$1@dont-email.me> <_CUMA.24965$kF7.13243@fx22.iad> <oe190e$c9f$1@dont-email.me> <oe27qv$pos$1@dont-email.me> <0d1f4017-9db3-4fd5-9f6d-0a9f1e1734f4@googlegroups.com> |
On 4/29/2017 11:34 PM, bill.sloman@ieee.org wrote: > On Sunday, April 30, 2017 at 12:29:55 AM UTC+10, rickman wrote: >> On 4/29/2017 1:44 AM, Don Y wrote: >> <<< snipped usual long winded stuff >>> >>> >>> By adding the NAND on the output of the counter (to synthesize the 4th >>> bit), >>> this period is *extended* by the propagation delay introduced by that gate. >>> Because the gate's *input* isn't stable until that previous mentioned time. >>> >>> This is only a problem if you expect the outputs to change simultaneously >>> (which would be a recipe for failure) and tried to decode individual, >>> specific "counts" with combinatorial logic on the outputs. >> >> Even the most basic digital logic books caution the reader against doing >> this because of the very long winded explanation below which can be >> summarized by "the outputs can't be decoded when they are changing >> because they don't all change at the same instant in time". > > Synchronous counters are a whole lot better than ripple counters in this respect. > > All the outputs change at once, all timed from the active edge of the clock. > > Table 7 of the Nexperia 74HC163 data sheet gives a typical propagation delay from clock to Q of 20nsec at Vcc=4.5V with a worst case of 37nsec. > > That leaves a window of about 30nsec when the outputs might be inconsistent, which is rarely long enough to matter. ??? What??? Maybe if you are lighting LEDs, but for driving other logic it can matter a great deal. If you need glitch free decoded outputs either they need to also be registered (which can be done without a clock delay by driving the decoder from the inputs to the counter register rather than the outputs) or you need to use a gray code counter such as a Johnson ring counter which can be decoded without glitches. -- Rick C
Back to sci.electronics.design | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-28 19:14 -0400
Re: Binary counter - please check my work Don Y <blockedofcourse@foo.invalid> - 2017-04-28 16:20 -0700
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-28 19:31 -0400
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-28 22:39 -0400
Re: Binary counter - please check my work Don Y <blockedofcourse@foo.invalid> - 2017-04-28 20:07 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 00:27 -0400
Re: Binary counter - please check my work Don Y <blockedofcourse@foo.invalid> - 2017-04-28 22:44 -0700
Re: Binary counter - please check my work Don Y <blockedofcourse@foo.invalid> - 2017-04-28 22:46 -0700
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-29 10:29 -0400
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 11:07 -0400
Re: Binary counter - please check my work bill.sloman@ieee.org - 2017-04-29 20:34 -0700
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-29 23:43 -0400
Re: Binary counter - please check my work bill.sloman@ieee.org - 2017-04-29 21:53 -0700
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-30 01:42 -0400
Re: Binary counter - please check my work bill.sloman@ieee.org - 2017-04-29 23:28 -0700
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-30 20:10 -0400
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-30 20:26 -0400
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-30 21:07 -0400
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-30 21:20 -0400
Re: Binary counter - please check my work bill.sloman@ieee.org - 2017-04-30 18:52 -0700
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-05-01 08:43 -0400
Re: Binary counter - please check my work krw@notreal.com - 2017-05-01 13:33 -0400
Re: Binary counter - please check my work bill.sloman@ieee.org - 2017-05-01 23:02 -0700
Re: Binary counter - please check my work Jasen Betts <jasen@xnet.co.nz> - 2017-05-02 11:42 +0000
Re: Binary counter - please check my work bill.sloman@ieee.org - 2017-05-02 06:10 -0700
Re: Binary counter - please check my work upsidedown@downunder.com - 2017-05-03 03:26 +0300
Re: Binary counter - please check my work pcdhobbs@gmail.com - 2017-05-02 18:41 -0700
Re: Binary counter - please check my work bill.sloman@ieee.org - 2017-05-02 19:39 -0700
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-05-02 11:30 -0400
Re: Binary counter - please check my work Jasen Betts <jasen@xnet.co.nz> - 2017-04-29 20:25 +0000
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-29 23:15 -0400
Re: Binary counter - please check my work upsidedown@downunder.com - 2017-05-01 11:12 +0300
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 00:43 -0400
Re: Binary counter - please check my work Winfield Hill <hill@rowland.harvard.edu> - 2017-04-29 05:31 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 09:48 -0400
Re: Binary counter - please check my work Don Y <blockedofcourse@foo.invalid> - 2017-04-29 08:45 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 12:51 -0400
Re: Binary counter - please check my work rickman <gnuarm@gmail.com> - 2017-04-29 14:54 -0400
Re: Binary counter - please check my work Don Y <blockedofcourse@foo.invalid> - 2017-04-29 12:34 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 15:51 -0400
Re: Binary counter - please check my work Don Y <blockedofcourse@foo.invalid> - 2017-04-29 21:37 -0700
Re: Binary counter - please check my work Jasen Betts <jasen@xnet.co.nz> - 2017-04-29 20:49 +0000
Re: Binary counter - please check my work Don Y <blockedofcourse@foo.invalid> - 2017-04-29 14:08 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 17:31 -0400
Re: Binary counter - please check my work Jasen Betts <jasen@xnet.co.nz> - 2017-04-30 00:51 +0000
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 21:42 -0400
Re: Binary counter - please check my work bloggs.fredbloggs.fred@gmail.com - 2017-04-29 12:17 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-29 15:36 -0400
Re: Binary counter - please check my work bloggs.fredbloggs.fred@gmail.com - 2017-04-30 08:00 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-30 11:13 -0400
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-30 11:24 -0400
Re: Binary counter - please check my work bloggs.fredbloggs.fred@gmail.com - 2017-04-30 08:30 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-04-30 16:06 -0400
Re: Binary counter - please check my work Jasen Betts <jasen@xnet.co.nz> - 2017-04-29 00:04 +0000
Re: Binary counter - please check my work bill.sloman@ieee.org - 2017-04-28 21:14 -0700
Re: Binary counter - please check my work stratus46 <stratus46@yahoo.com> - 2017-05-01 01:51 -0700
Re: Binary counter - please check my work stratus46 <stratus46@yahoo.com> - 2017-05-01 01:56 -0700
Re: Binary counter - please check my work bitrex <bitrex@de.lete.earthlink.net> - 2017-05-01 13:36 -0400
csiph-web