;  demo interrupt on s21
;      increment count by interrupt service routine

.symbol
  cnt   100      ; global counter

.code 0
:main
  mov r1 #isr
  st r1 1000     ; set int vector at M[1000]
  mov r1 #200
  trap r1 #13    ; set timer0 200
  mov r1 #0
  st r1 cnt      ; global cnt
:while
  trap r0 #17    ; sleep wait int
  jmp while

:isr             ; int service routine
  ld r1 cnt
  add r1 r1 #1
  st r1 cnt
  trap r1 #1     ; print cnt
  reti

.data 100
.end