[email protected] said: > On the other hand, it would not be difficult to make a DDS which hit 60/ > 10000000 exactly. Reducing it by 20 on each side you get 3/500000 so a 19 > bit accumulator (mod 500000) incrementing with 3 on every 100 ns period > would do it.
Neat. Thanks. I'd noticed that adding in decimal rather than binary would make exact target frequencies in some cases, but I hadn't generalized to adding modulo N. Using N of 10,000,000 with a 10 MHz clock gets you all exact integer frequencies in the audio range. > A LUT for sine would be possible. Playing a few tricks with the LUT table > (realizing that the LUT would be walked through three times with three > different start-alignments) converts it into a LUT of the same size and a > increment by one or decrement by one counter modulus 500000. A decrement by > one counter allows wrap-around loading with 499999 easy. CPLD or CMOS/TTL > implementations would be trivial for the counter. The LUT will be large... More neat. Thanks again. It's just a simple state machine cycling through some collection of states. If we are willing to rearrange the LUT/ROM, we can simplify the next state calculation from a modulo adder to a re-loadable counter. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
