// show interrupt mode

//   similar to ems-demo plot routine
//   14 Jan 2013

// dummy header for compiler use
asm(x)

// ISR, assembly
// x is r1, y is r2, color is r3

int_plot()
  asm("st r1 1010")
  asm("st r2 1011")
  asm("trap r3 #15")  
  asm("add r1 r1 #1")
  asm("add r2 r2 #1")
  asm("sub fp fp #1")  // correct fp
  asm("ret r31")

main()
//  setup interrupt
  asm("mov r1 #int_plot")
  asm("st r1 1000")
  asm("mov r1 #1")
  asm("trap r1 #12 ; enable int")
  asm("mov r1 #100")	
  asm("trap r1 #100 ; set timer1 = 100")
  asm("mov r1 #100")
  asm("trap r1 #11  ; set div = 100")

  x = 10
  y = 10
  color = 1
  while(x < 50)
    // empty loop
    // use ISR to plot and step x,y