We are using an ATSAMD51P19A and the Timer/Counter for Control Applications (TCC) to detect the pulse width from the assertion of a pin to the detection of a signal on another pin, and are having trouble achieving our desired resolution of +/- 10 nsec.
The below block diagram shows our Atmel START configuration to capture the pulse width.
Using a delay generator, we know the time delta from the assertion of the pin PA23 to the rising edge of the pin PA22 is 720 nsec +/- 5 nsec. Given our configuration, we expected that we could capture a pulse width of 720 nsec +/- 10 nsec. However, we are seeing 720 nsec +/- 50 nsec. Our application requires +/- 10 nsec, so the +/- 50 nsec is undesirable.
We have tried many configurations and have been unable to achieve an accuracy better than +/- 50 nsec. Any suggestions or feedback on how to achieve a higher resolution would be greatly appreciated.