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Re: fast divider?

Cross-posted to 2 groups.

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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.

-- 
Bill Sloman, Sydney

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Thread

fast divider? john larkin <jl@glen--canyon.com> - 2026-03-15 11:47 -0700
  Re: fast divider? someone <cffbf4deb9142bce48974efc0e64dede@example.com> - 2026-03-17 22:30 +0000
    Re: fast divider? john larkin <jl@glen--canyon.com> - 2026-03-19 10:05 -0700
      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? 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? 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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