I have just changed my code to:

Code:
  PULSIN PORTD.6,1,rlow                             
  PULSIN PORTD.6,0,rhigh                            
  rtotal = (rhigh + rlow) / 10
  tbase = 500 * 600
  rpm = div32 rtotal
  if rpm = 65535 then
    rpm = 0
  endif
and I am displaying rtotal on my LCD, which when rlow and rhigh are at 1400, rtotal is at 280. Exactly what I expect. The problem is in the next 2 lines. 500 * 600 should be 300,000. Which when divided by 280, should give me 1071.

But instead I get 0rpm (obviously caused by the following if statement intended to show me 0rpm if the engine is not running)