Re: fast divider?

From	Bill Sloman <bill.sloman@ieee.org>
Newsgroups	sci.electronics.design, comp.arch.fpga
Subject	Re: fast divider?
Date	2026-03-30 16:42 +1100
Organization	A noiseless patient Spider
Message-ID	<10qd2fk$26ddd$1@dont-email.me> (permalink)
References	(6 earlier) <cajdskhquqlkq5p7k0o4u99v39kr18nj4q@4ax.com> <10q7psn$atug$5@dont-email.me> <7higskpevth1a4ced39pp3tihtu8dvadi7@4ax.com> <10qab75$171gk$1@dont-email.me> <mofiskhb78kfo79v5b0ll51mjp5bb68sqk@4ax.com>

Cross-posted to 2 groups.

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On 30/03/2026 2:18 am, john larkin wrote:
> On Sun, 29 Mar 2026 15:52:53 +1100, Bill Sloman <bill.sloman@ieee.org>
> wrote:
> 
>> On 29/03/2026 8:38 am, john larkin wrote:
>>> On Sat, 28 Mar 2026 16:44:40 +1100, Bill Sloman <bill.sloman@ieee.org>
>>> wrote:
>>>
>>>> On 28/03/2026 5:39 am, john larkin wrote:
>>>>> On Sun, 22 Mar 2026 03:00:16 +1100, Bill Sloman <bill.sloman@ieee.org>
>>>>> wrote:
>>>>>
>>>>>> On 22/03/2026 1:52 am, john larkin wrote:
>>>>>>> On Sat, 21 Mar 2026 16:36:43 +1100, Bill Sloman <bill.sloman@ieee.org>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> On 20/03/2026 4:05 am, john larkin wrote:
>>>>>>>>> On Tue, 17 Mar 2026 22:30:01 +0000, someone
>>>>>>>>> <cffbf4deb9142bce48974efc0e64dede@example.com> wrote:
>>>>>>>>>
>>>>>>>>>> I assume these are up-counters, so the thing overflows at all 1's. Then you only have the one fast carry TPD for the MS18b overflowing to all 1s when a 1 is clocked into its LSB.  One whole clock period to clock the 1 out of the DFF and meet the setup times for what I assume is a synchronous LD and its setup for the counters. So that particular timing criticality is a DFF TPD and a LD setup TSU to reliably capture the register data. The LD TPD to CLK TSU for the LS18b counter shouldn't be a problem. This must be very speedy logic for 150MHz. Do you have a simulator that displays how much margin you have on this timing, or is it just a bunch waveforms?
>>>>>>>>>
>>>>>>>>> Yes, loadable up-counter with carry chain.
>>>>>>>>>
>>>>>>>>> This would be in an FPGA, so the diagram is just a concept. The
>>>>>>>>> reality will be VHDL code. And the FPGA boys use the Wishbone
>>>>>>>>> architecture and want the counter to be 32 bits, which is OK with me.
>>>>>>>>>
>>>>>>>>> We are already doing a DDS at 250 MHz on this chip, an Efinix T20, so
>>>>>>>>> I expect we could do a divider in that ballpark.  The T20 is in the
>>>>>>>>> *slow* Efinix family.
>>>>>>>>>
>>>>>>>>> I think the T20 has 18-bit fast carry chains.
>>>>>>>>>
>>>>>>>>> After the boys code this, the tools can verify timing.
>>>>>>>>>
>>>>>>>>> FPGAs are great, but there's a cultural gap between people who draw
>>>>>>>>> and people who type.
>>>>>>>>
>>>>>>>> Can't say I've noticed that, but since I can do both, and most of the
>>>>>>>> engineers I've hung out with could too, John Larkin may be projecting here.
>>>>>>>
>>>>>>> Gosh Bill, you are wonderful. You are great at everything.
>>>>>>
>>>>>> I'm certainly not great at writing VHDL. There's a VHDL text-book on my
>>>>>> bookshelf - bought for a project which didn't come off - but the stuff I
>>>>>> did type was in a much less powerful language, but powerful enough to
>>>>>> get the chip to do what I wanted it to.
>>>>>>
>>>>>>> What are you designing now?
>>>>>>
>>>>>> Absolutely nothing. I do fish for work from time to time, but at 83 I'm
>>>>>> not an attractive employee.
>>>>>
>>>>> Join one of those maker space things, meet some people, offer to help
>>>>> for free, see what happens.
>>>>
>>>> I'm active on the committee of NSW branch of the IEEE but I don't know
>>>> of any maker space things in Sydney.
>>>
>>> Hey, you could google
>>>
>>> maker spaces sydney australia
>>
>> https://makerspaces.com.au/nsw/sydney
>>
>> So they exist. Leather work and needle work (sewing) are supported. I am
>> a tolerably competent carpenter so I might fit in. As a route into
>> advanced electronic design it doesn't look promising.
> 
> We have some of that handicraft stuff here, but we have a lot of
> people who want to build things that use electronics, and those people
> aren't usually very good circuit designers. [1]
> 
> Some of them are actual startups with an idea and some funding. They
> go to meetups to pitch their ideas and maybe meet people who could
> help.
> 
> Studio 45 near here has an occasional meetup with 500 people, free
> food and beer. We might sponsor one.
> 
> We had a cool one at a Rivian facility. I met a photonics consultant
> and recommended Phil's book. And listened to yet another pitch for AI
> circuit/pcb design.
> 
> There's one coming up in a pier on the SF Bay, an ocean
> instrumentetion outfit. That should be fun.
> 
> I do one or two meetups per month and meet lots of Young Things.
> 
> The point is that you could show up, and meet people who need
> electronics, and see what happens.

If I showed up at the right meetings, I might meet people who needed 
electronics. The odds don't look great.

> Or don't.

That would seem to be the rational choice.

> [1] It's impressive how few people are good at electronic design.

Even more impressive that you seem to think you can make that statement.
If you don't think that a classical emitter-coupled monostable can work, 
your status as a judge of electronic design quality can't be all that high.

-- 
Bill Sloman, Sydney

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Thread

Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-21 16:36 +1100
  Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-21 07:52 -0700
    Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-22 03:00 +1100
      Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-27 11:39 -0700
        Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-28 16:44 +1100
          Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-28 14:38 -0700
            Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-29 15:52 +1100
              Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-29 08:18 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-30 16:42 +1100
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-30 08:00 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-31 16:35 +1100
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-31 02:40 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-31 22:30 +1100
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-31 08:14 -0700
                Re: fast divider? Buzz McCool <buzz_mccool@yahoo.com> - 2026-03-31 10:41 -0700
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-31 10:57 -0700
                Re: fast divider? Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-03-31 14:25 -0700
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-31 15:16 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-01 16:17 +1100
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-01 16:05 +1100
                Re: fast divider? Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-04-01 02:04 -0700
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-01 07:25 -0700
                Re: fast divider? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-04-01 16:07 +0000
                Re: fast divider? Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-04-01 09:37 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-01 15:54 +1100
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-01 01:06 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-02 02:13 +1100
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-01 09:12 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-02 14:41 +1100
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-02 07:53 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-03 02:21 +1100
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-02 08:57 -0700
                Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-04-03 04:05 +1100
                Re: fast divider? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-04-02 13:17 -0400
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-02 11:20 -0700
                Re: fast divider? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-04-09 10:55 -0400
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-09 10:34 -0700
                Re: fast divider? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-04-09 13:43 -0400
                Re: fast divider? John R Walliker <jrwalliker@gmail.com> - 2026-04-09 19:07 +0100
                Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-04-09 13:47 -0700
    Re: fast divider? someone <cffbf4deb9142bce48974efc0e64dede@example.com> - 2026-03-26 23:30 +0000
  Re: fast divider? Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-03-21 09:38 -0700
    Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-21 10:29 -0700
      Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-23 23:49 +1100
        Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-23 08:20 -0700
          Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-24 23:04 +1100
            Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-24 05:56 -0700
              Re: fast divider? Bill Sloman <bill.sloman@ieee.org> - 2026-03-25 02:47 +1100

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