the OP have`nt mentioned the frequency of incoming signal from that only i assumed the signal might be of low freuencyand if so the comparator will get out of saturation (but again that depends on the frequency)and as far as noise is concerned a positive feed back resistor could be added for hysterisis but how much hysterisis that depends on aplication...as i also works on microchip PIC devices the above of two situatuions never exists because the externaly interrupt pins uses schemit triggers and can be cogfigure for interrupt on rising or falling edge through software on fly.

PS:this was just to give some idea solely with purpose of help so that OP may get some help...more things can be eloborated by one of our forum member Mr Kai who is an expert at analog electronics,by the way thanks mr Eric for comments as this is the only way i see we juniors will move forward having seniors like you,thanks.

SAIF ULLA KHALID