dos33fsprogs/keyboard/keyboard.s
2024-04-09 00:02:19 -04:00

32 lines
492 B
ArmAsm

; HARDWARE LOCATIONS
KEYPRESS = $C000
KEYRESET = $C010
KEYSTROBE = $C010
; on original Apple II/II+
; read KEYPRESS
; if bit 7 set, means key was pressed, value in lower 7 bits
; access KEYSTROBE to clear value and allow another keypress to happen
; on Apple IIe
; can read KEYSTROBE. bit 7 is "any key is down"
; test keyboard
keyboard:
ldy #0
keyboard_loop:
lda KEYPRESS
bpl keyboard_loop
ora #$80
sta $400,Y
iny
bit KEYRESET
jmp keyboard_loop