Yes, shortly after having sent out the message I realized that I was, as usual, too fast. I'm aware that a simple microprocessor can't be used but a Spartan3 can be involved. Then another problem: the 2.048MHz is about 1/5 of the 10MHz so it is not possible. Sofar the way out is: dividing the 10MHz by 625 and then multiplying by 128 using the DCM in the Spartan3... but nothing clever in this method. Sorry, not a valid contribution.
On Thu, Feb 2, 2012 at 6:07 PM, Tom Van Baak <t...@leapsecond.com> wrote: > Azelio, > > 2.048 MHz has a cycle period of just 488.28125 ns so a PIC/AVR is (far) > too slow to use the same trick I did on the low frequency 32 kHz. > > I think you'll have to use a PLL for that one. How about a 16 kHz compare > rate: 10 MHz / 625 = 16000 Hz = 2.048 MHz / 128 > > /tvb > > ----- Original Message ----- > From: Azelio Boriani > To: Tom Van Baak ; Discussion of precise time and frequency measurement > Sent: Thursday, February 02, 2012 8:18 AM > Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video > recorders > > > Amazing... there is always something to learn from TVB. Now I'll try to > derive a 2.048MHz G.703-13 clock from a 10MHz clock. I suspect that the > procedure is similar, even if 2048KHz is not quite a power of 2. > > > On Thu, Feb 2, 2012 at 4:35 PM, Tom Van Baak <t...@leapsecond.com> wrote: > > Hi Roberto, > > The motivation for this, I assume most list members know, is to > drive cheap quartz stepper motor clocks with precise 32 kHz > frequency, one derived from an atomic or GPS 10 MHz. > > The 10 MHz to 32 kHz PIC divider I wrote uses a sort of binary > "leap year" algorithm to adjust the digital output phase to be as > close as possible to the ideal 32.768 kHz phase on each cycle > and also to have zero long-term error. > > I'm not sure how well a multi-level leap year algorithm relates > Breseham's algorithm. I tracked down his 1965 plotter article. > There might be common ground there. > > With non-integral ratios like this case, or without external analog > components (e.g., PLL), it seems some level of jitter is always > unavoidable. So the goal was to make it as mathematically small > as possible, and furthermore, to be able to do the math within a > half cycle, which is only 15 microseconds. > > I'll send you an early draft of the PIC code; the version that was > most clear before I had to pinch too many cycles and added too > many features. Let me know what you think. > > I also simulated the algorithm on a PC and measured the ADEV > and phase noise. That simulation code is file 10m32k.c under: > > http://www.leapsecond.com/tools/ > > /tvb > > ----- Original Message ----- From: "Roberto Barrios" <rbarri...@msn.com > > > To: "Tom Van Baak" <t...@leapsecond.com>; "Discussion of precise time > and frequency measurement" <time-nuts@febo.com> > Sent: Thursday, February 02, 2012 5:09 AM > Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video > recorders > > > > Hi Tom, > > I'm interested in that divider. Actually, insterested in knowing how > it works, not in the .HEX file. > > Breseham's algorith works but has inherent jitter and I've found no > other solutions for situations like that. > > I'd live to know how it is done. > > Thank you, > Roberto EB4EQA > http://www.rbarrios.com > > > -----Mensaje original----- From: Tom Van Baak > Sent: Thursday, February 02, 2012 10:34 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video > recorders > > > I think I've seen comments about making 32 KHz from 10 MHz in a PIC > or AVR. > > tvb has this web page, but I don't see a 32 KHz option: > http://www.leapsecond.com/pic/picdiv.htm > > > Hal, > > Yes, I have a PIC divider that takes 5 or 10 MHz input and > outputs a 32.768 kHz square wave with minimal jitter and > no long-term phase offset. Contact me off-line if interested. > > /tvb > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.