.globl _start
_start:
+ ;; set port a to output
+ ldab #0xfc ; 11111000
+ stab 0x1001
+
+ ;; start chiming
+ ldx #0x1000
+ bset 00,x #0x10
+
;; enable the RTI
ldaa #0x40
staa 0x1024
;; set RTI intervals, and PA3/7 DDRs
ldaa #0x81
- staa 0x1026
+ staa 0x1026 ;; RTI interval becomes E/2^14 = 6.6ms (or 150 Hz)
;; clear ADC register
clra
staa 0x1030
;; set the stack pointer
- lds _stack
+ lds #_stack
;; blank initialised variables - should match memory.x's page0
ldx #0x0000
loop1:
- cpx #0x0080
+ cpx #0x0100
bcc out1
clr 00,x
inx
bra loop1
out1:
+ ;; stop chiming
+ ldx #0x1000
+ bclr 00,x #0x10
+
jsr main
infinity: