Test of copying between VERA data0 and data1 where address of data0 is altered between copy's

vmem_copy.asm

!cpu w65c02
!macro SYS_LINE .main {
*=$801
	!word	.next_line		; Pointer to next BASIC line
	!word	$000A			; Line number $000A = 10
	!byte	$9E			; SYS BASIC token
	!byte	48+(.main/1000)%10	; Address where ASM starts in PETSCII
	!byte	48+(.main/100)%10
	!byte	48+(.main/10)%10
	!byte	48+(.main/1)%10
	!byte	$00			; End of BASIC line
.next_line:
	!word	$0000			; End of BASIC program
}

vaddrl = $9F20
vaddrm = $9F21
vaddrh = $9F22

data0 = $9F23
data1 = $9F24

vctrl = $9F25

+SYS_LINE main

main:
	jsr	setupvmem

        lda     vctrl   ; Select DATA0
        and     #$FE
        sta     vctrl

        lda     #$10    ; Data0 increment1, bank 0
        sta     vaddrh
        stz     vaddrl  ; Data0 points to $00100
        lda     #$01
        sta     vaddrm

        lda     vctrl   ; Select DATA1
        ora     #$01
        sta     vctrl

        lda     #$10    ; Data1 increment1, bank 0
        sta     vaddrh

        stz     vaddrl  ; Data1 points to $01000
        lda     #$10
        sta     vaddrm

	lda	data0	; Copy from data0 to data1
	sta	data1
	lda	data0
	sta	data1

        lda     vctrl   ; Select DATA0
        and     #$FE
        sta     vctrl
        stz     vaddrl  ; Data0 points to $00200
        lda     #$02
        sta     vaddrm

        lda     data0   ; Copy from data0 to data1
        sta     data1
        lda     data0
        sta     data1

	rts

setupvmem:
	lda	vctrl	; Select DATA0
	and	#$FE
	sta	vctrl

	lda	#$10	; Data0 increment1, bank 0
	sta	vaddrh
	stz	vaddrl	; Data0 points to $00100
	lda	#$01
	sta	vaddrm

	lda	#$aa
	sta	data0
	sta	data0

	lda	#$02	; Data0 points to $00200
	sta	vaddrm
	stz	vaddrl

	lda	#$bb
	sta	data0
	sta	data0
	rts

Build with: acme -f cbm -o VMEMCOPY.PRG vmem_copy.asm