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Created page with "This is a collection of simple examples of 6502 code which will run in the emulator. == Fill the Bitmapped Display == lda #$00 ; set pointer..."
This is a collection of simple examples of [[6502]] code which will run in the [[6502 Emulator|emulator]].
== Fill the Bitmapped Display ==
lda #$00 ; set pointer at $10 to $0200
sta $10
lda #$02
sta $11
ldx #$06 ; max value for $11
ldy #$00 ; index
loop: sta ($10),y ; store colour
iny ; increment index
bne loop ; branch until overflow
inc $11 ; increment hi byte of pointer
lda $11 ; load page number as colour
cpx $11 ; compare with max value
bne loop ; continue if not done
rts ; return
== Place a Message on the Character Display ==
define SCREEN $f000
ldy #$00
char: lda text,y
beq done
sta SCREEN,y
iny
bne char
con e: brk
text:
dcb "6","5","0","2",32,"w","a","s",32,"h","e","r","e",".",00
== Type on the Screen ==
; let the user type on the first page of character screen
; has blinking cursor!
; backspace works, arrows and ENTER do not
next: ldx #$00
idle: inx
cpx #$10
bne check
lda $f000,y
eor #$80
sta $f000,y
check: lda $ff
beq idle
ldx #$00
stx $ff
cmp #$08 ; bs
bne print
lda $f000,y
and #$7f
sta $f000,y
dey
jmp next
print: sta $f000,y
iny
jmp next
== Fill the Bitmapped Display ==
lda #$00 ; set pointer at $10 to $0200
sta $10
lda #$02
sta $11
ldx #$06 ; max value for $11
ldy #$00 ; index
loop: sta ($10),y ; store colour
iny ; increment index
bne loop ; branch until overflow
inc $11 ; increment hi byte of pointer
lda $11 ; load page number as colour
cpx $11 ; compare with max value
bne loop ; continue if not done
rts ; return
== Place a Message on the Character Display ==
define SCREEN $f000
ldy #$00
char: lda text,y
beq done
sta SCREEN,y
iny
bne char
con e: brk
text:
dcb "6","5","0","2",32,"w","a","s",32,"h","e","r","e",".",00
== Type on the Screen ==
; let the user type on the first page of character screen
; has blinking cursor!
; backspace works, arrows and ENTER do not
next: ldx #$00
idle: inx
cpx #$10
bne check
lda $f000,y
eor #$80
sta $f000,y
check: lda $ff
beq idle
ldx #$00
stx $ff
cmp #$08 ; bs
bne print
lda $f000,y
and #$7f
sta $f000,y
dey
jmp next
print: sta $f000,y
iny
jmp next
