Re: fast divider?

From	john larkin <jl@glen--canyon.com>
Newsgroups	sci.electronics.design, comp.arch.fpga
Subject	Re: fast divider?
Date	2026-03-28 14:38 -0700
Organization	A noiseless patient Spider
Message-ID	<7higskpevth1a4ced39pp3tihtu8dvadi7@4ax.com> (permalink)
References	(3 earlier) <10plapt$26c7q$6@dont-email.me> <a7btrkdp0apjrc7hbkat4p5um1o635pti2@4ax.com> <10pmfb0$2gmh7$5@dont-email.me> <cajdskhquqlkq5p7k0o4u99v39kr18nj4q@4ax.com> <10q7psn$atug$5@dont-email.me>

Cross-posted to 2 groups.

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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


John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics

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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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