An all-digital GPS disciplined oscillator using MMCM phase shift.
Using a BASYS3 development board, if a GPS module's PPS input is connected to JB0 clk signal will be soon be locked to the GPS system's time reference. LEDs 14:0 show the current error in HZ, and LED15 show if it is locked.
Well, by locked I mean it will have a frequency that is kept within one part per million of GPS time.
The control loop is woefully engineered, and the size of all the registers has been (not) optimized for coding simplicity, and all the constants are empirically derived, but it works as advertised.
Plenty of room for experiment and improvement.