SCRUB

: SRF05 
  TA0 OFF TA0 ON TA0 OFF ( PULSE OUT
  TA0 ON                 ( MAKE HIGH TO BE INPUT
  TA0 SET-PWM-IN         ( READY TO READ PULSE WIDTH
  BEGIN 
    CHK-PWM-IN           ( CHK PULSE
    ?DUP                 ( DUP IF NON ZERO
  UNTIL .                ( STOP WAITING WHEN NON ZERO, PRINT
;