21 lines
421 B
ArmAsm
21 lines
421 B
ArmAsm
; Function defined on pp272-273 of C64 Programmers Reference Guide
|
|
stop:
|
|
;; Bit 7 of BUCKYSTATUS contains the state of the STOP key
|
|
;; (Compute's Mapping the 64, p27)
|
|
|
|
;; BASIC checks carry flag to indicate STOP or not
|
|
lda BUCKYSTATUS
|
|
and #$80
|
|
beq stop_pressed
|
|
|
|
;; By trial and error, we know that Z + C = BREAK
|
|
;; and that neither should be set otherwise
|
|
lda #$ff
|
|
clc
|
|
rts
|
|
|
|
stop_pressed:
|
|
sec
|
|
lda #$00
|
|
rts
|