39 lines
507 B
ArmAsm
39 lines
507 B
ArmAsm
.code
|
|
|
|
LEDS = $efff
|
|
TIMER_BASE = $eff8
|
|
TIMER_DIVISOR = 5
|
|
|
|
TIMER_OLD = $10
|
|
|
|
main:
|
|
lda #$ff
|
|
sta TIMER_BASE+TIMER_DIVISOR
|
|
lda TIMER_BASE
|
|
sta TIMER_OLD
|
|
stz LEDS
|
|
|
|
|
|
; load the new value of the timer in a
|
|
; subtract the old value of the timer
|
|
; if the result is greater than 30, then do something
|
|
|
|
loop:
|
|
lda TIMER_BASE
|
|
tax
|
|
sec
|
|
sbc TIMER_OLD
|
|
sec
|
|
sbc #$20
|
|
bcc loop
|
|
|
|
stx TIMER_OLD
|
|
inc LEDS
|
|
bra loop
|
|
|
|
.segment "VECTORS"
|
|
|
|
.addr main
|
|
.addr main
|
|
.addr main
|