;Interrupt example
             ;
             CONSTANT waveform_port, 02             ;bit0 will be data
             CONSTANT counter_port, 04
             CONSTANT pattern_10101010, AA
             NAMEREG sA, interrupt_counter
             ;
      start: LOAD interrupt_counter, 00             ;reset interrupt counter
             LOAD s2, pattern_10101010              ;initial output condition
             ENABLE INTERRUPT
             ;
 drive_wave: OUTPUT s2, waveform_port
             LOAD s0, 07                            ;delay size
       loop: SUB s0, 01                             ;delay loop
             JUMP NZ, loop
             XOR s2, FF                             ;toggle waveform
             JUMP drive_wave
             ;
             ADDRESS 2B0
int_routine: ADD interrupt_counter, 01              ;increment counter
             OUTPUT interrupt_counter, counter_port
             RETURNI ENABLE
             ;
             ADDRESS 3FF                            ;set interrupt vector
             JUMP int_routine