;Interrupt example
             ;
             constant waveform_port, $02             ;bit0 will be data
             constant counter_port, $04
             constant pattern_10101010, $AA
             register interrupt_counter, $a
             ;
      start: load interrupt_counter, 00             ;reset interrupt counter
             load s2, pattern_10101010              ;initial output condition
             interrupt enable
             ;
 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 $B0
int_routine: add interrupt_counter, 1              ;increment counter
             output interrupt_counter, counter_port
             returni enable
             ;
             address $FF                             ;set interrupt vector
             jump int_routine