Direct Digital Synthesis[1] - it is almost trivial... you just accumulate phase with an adder that is much longer than the output resolution, you take the top b

Direct Digital Synthesis[1] - it is almost trivial... you just accumulate phase with an adder that is much longer than the output resolution, you take the top bits and feed them into a sine lookup, and you can generate a sine wave of arbitrary frequency and phase. The amazing part is that it is common to have resolution of 1/100 of a Hertz on RF signals. Correcting frequency to lock to WWV is trivial bit of math. Long ago, I had a 68HC11 processor with 512 bytes of EEPROM to store my program into, part of it was locking on to the speed of a production line, with a pulse that happened about every 15 inches (one revolution of the drive wheel) and adjusting timing in a simulated phase locked loop to get 1/10" counts. I had an DDS in there along with all the other code and it worked great. That part of it was about 50 bytes, if I recall correctly. [1] https://en.wikipedia.org/wiki/Direct_digital_synthesis https://en.wikipedia.org/wiki/Direct_digital_synthesis