.makeexe

        jump    start

// we need an interrupt vector
inters: .space  20

timhand:        // timer interrupt handler
        type    '.'
// restart timer
        load    r1, 20000
        setsr   r1, $timer
// special return to restore everything
        iret

start:
// say where the interrupt vector is
        load    r1, inters
        setsr   r1, $intvec

// put handler in interrupt vector
        load    r2, timhand
        store   r2, [r1 + iv$timer]

// allow interrupts but saying NOT processing one now
        load    r1, 0
        setfl   r1, $ip

// set a timer
        load    r1, 20000
        setsr   r1, $timer

slow:   load    r1, 80
        load    r2, 0
loop:   add     r2, 1
        pause
        sub     r1, 1
        jpos    r1, loop
        halt