t...@leapsecond.com said: > 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.
It's the same math as a DDS. If Breseham would land exactly on a grid point after N steps, a DDS will have no long term drift. That means the slope of the Breseham line is N/M where both N and M are integers. For the intermediate steps, both Breseham and DDS come as close as possible: 1/2 grid spacing vs 1/2 clock period. We usually think of DDS as requiring M to be a power of 2 but you don't have to do it that way. One obvious example is to make M a power of 10 by doing decimal adds rather than binary. That should work well with a FPGA but I haven't done it yet. If you start with 10 MHz, that will give you perfect hits on integer audio frequencies. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ 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.
