[time-nuts] Features of a Precision Clock?
James Maynard
james.h.maynard at usa.net
Thu Oct 5 16:13:47 EDT 2006
On receipt of Bulletin C, can you arm this clock to display the upcoming
leap second? That's a feature that I would desire.
Brooke Clarke wrote:
> Hi:
>
> I've got the Precision Clock to work and have some questions about the
> priority of the features. As it is now the clock allows user selection
> of the input frequency at power up that determines the instruction clock
> for the PIC micro controller. The choices are 2.5, 5, 10 or 20 Mhz.
> The clock displays on line one HH:MM:SS and on line two Day of Week,
> YYYY, Mon, Day of Month. The leap year testing uses the 4, 100 and 400
> year rules and so you can determine the day of the week for any Georgian
> calendar (1583 onwards) date.
>
> Setting is by means of 4 buttons, Right, Left, Increment, Decrement.
> This is very intuitive and quick. During setting the clock continues to
> keep time. Also a new data field to the right of the seconds appears as
> 4 hex digits to allow moving the LED/1 PPS output pulse in 1 ms steps.
>
> If the input frequency fails then all the fields that can blink do blink
> and the clock stops. Pressing and holding Right or Left for a few
> seconds clears the blinking and restarts the clock using the input
> frequency that was selected at power up.
>
> For more see:
> http://www.pacificsites.com/~brooke/PRC68COM.shtml#PC3
>
> Now for the possible next features to be added. It would be nice to get
> some feel for how important they are:
>
> (1) Synchronize the 1 PPS output rising edge to be near a 1 PPS input
> pulse on a one time basis (the 1 PPS edge will have an error of a few
> instruction cycles which are each 4/Fin long). If this was done the
> manual setting would be removed.
>
> (2) Add another mode of operation where the clock runs on it's internal
> RC oscillator and the timing is determined by an external 1 PPS that
> needs to always be connected.
>
> (3) Add a backup Real Time Clock with it's own coin cell battery to
> allow using the clock in a portable application and allow the clock to
> be shipped while running. The chip has a 0.1 ppm aging trim capability
> and there could be a provision to automatically trim it when one of the
> above precision input frequencies is applied for maybe a day. Then when
> the input frequency is disconnected the clock would continue to tell the
> time. There are also many options for alarms.
>
> (4) Other displays such as fractional Julian Day number, fractional
> Modified Julian Day number. sidereal time, or ???
>
> I don't think there's enough memory for all of the above, probably only
> one or two of them so I'm hoping to get some input on the priorities.
>
> Have Fun,
>
> Brooke Clarke
>
--
James Maynard
Salem, Oregon, USA
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