[time-nuts] What's the easiest way to divide by 10 for Thunderbolt reference output?

John Ackermann N8UR jra at febo.com
Tue Jul 24 21:21:02 UTC 2012


TVB can give a better answer, but in general the number of clock cycles 
required per instruction limits the minimum divide ratio.

Tom whipped up a special PIC to get the highest possible output rate for 
a set of tests we were doing, and given the 20 MHz maximum input clock, 
we got about 800 kHz output.

John
---

On 7/24/2012 1:05 PM, Chris Hoffman, KG6O wrote:
> John,
>
> That's interesting to me. What exactly are the actual structural limitations of [that] pic?
>
> -CH
>
> On Jul 24, 2012, at 7:55, John Ackermann N8UR <jra at febo.com> wrote:
>
>> Unfortunately, the TAPR T2-Mini divider (http://www.tapr.org/kits_t2-mini.html) can't quite get to 1 MHz from 10 MHz with the PIC divider chip due to limitations in the chip architecture.
>>
>> However, nothing says you couldn't "dead bug" in a decade divider chip in place of the PIC, and let the T2-Mini provide the input conditioning, output driver, voltage regulation, connectorization, etc. for you, making it much a smaller project.
>>
>> John
>> ----
>>
>> On 7/24/2012 8:18 AM, Chris Wilson wrote:
>>>
>>>
>>>    24/07/2012 13:14
>>>
>>> My Racal Dana 9908 can take a 1 Mhz external reference. Inputting my
>>> Thunderbolt at 10 MHz works, but shifts the decimal point over. I am
>>> not sure if this has any other detrimental effects as to accuracy or
>>> other? What's the easiest way to have a 1 MHz reference from the
>>> Thunderbolt for this timer / counter please, yet retaining 10 Mhz for
>>> my other devices that want a 10MHz reference signal?  Thanks.
>>>
>>
>>
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