Abhishek -

I guessed that he would be using assembly, and hoped the signal period would fall within the range of a single 16-bit timer overflow. My approach would not need any greater-than or less-than comparison to code in assembly, so I thought it might be easier to implement.

Your pulsewidth measurement approach, followed by a comparison against a threshold value is a better approach. I suppose if the pulsewidth is a multibyte value, you could simply check the highest byte. That would probably give adequate resolution for an app like this and is easy to code.

- Lee