James,
     My HP gets 1ppb of course I don't expect any thing close to that.=20
Like I said 1ppm would be great. OK, no resonator. A crystal is no=20
problem. Timers sound better but more difficult. And it is the timer=20
that I don't how to setup to get my one second pulse on demand.
     The reset pulse is easy. Just output the high for one or two=20
instruction cycles. The part that I'm not getting is how to wait for=20
whatever amount of time that corresponds to the wishes of the user for=20
the length of time to display the reading. Sometimes when I am using my=20
HP freq counter I like to have a very fast display refresh. At other=20
times I want the count to stay up for a much longer time period before=20
it is refreshed.
     The reset pulse of 20ns or longer occurs when the display should be=20
refreshed. Then the one second pulse is output to open the count gate.=20
Now we wait for a certain length of time so that the user can read the=20
display and then we output the reset pulse and open the counting gating=20
and do this over and over. But how? I know what I want to do and the=20
order to do them in but I don't know how. I know that the configuration=20
fuses have to be set, then setup the ADC, setup the timer or timers, and=20
finally enter the loop. Is that it?
Thanks,
rich!

On 7/18/2014 3:38 AM, James Cameron wrote:
> On Fri, Jul 18, 2014 at 03:20:06AM -0500, Richard R. Pope wrote:
>>       I'm replying to myself because it is the part about controlling
>> the one second pulse that I just don't know how to do. Do I use a
>> timer or do I setup a set of delay loops. The more accurate the one
>> second pulse the more accurate that the frequency being displayed is
>> going to be.
> Exactly.  What you haven't yet said is how accurate you want the pulse
> to be, and what else the microcontroller is going to be doing.
>
> If it is doing nothing else, delay loops will be fine.
>
> If it is doing other things, use a timer.
>
> At the end of the day, these two methods are almost identical.
>
> Regardless, you have to know, from the top down in your design, how
> much variation you will accept in your pulse frequency.
>
> The variation in both delay loops and timer will depend on your
> crystal and thermals.  I wouldn't think of using a resonator.
>

--=20
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