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; Test VIA's PORTB using alternating bit pattern.
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	processor 6502	; Processor directive for Assembler.

PORTB = $6000	; Our data port (Port B).
PORTA = $6001	; Our control port (Port A).
DDRB =  $6002	; Data Direction Register for Port B. 1: output, 0: input.
DDRA =  $6003	; Data Direction Register for Port A.
Reset = $8000	; Reset vector address of $8000 (start of ROM).

	;seg .U code
	org $8000	; Define the code origin of $8000 (ROM) starting point.
	
Start:
	lda	#$FF	; A9 FF		; All pins will be outputs.
	sta	$DDRB	; 8D 02 60	; DDRB: Data Direction Register for port B.
	
Loop:	
	lda	#$55	; A9 55		; Odd-bits pattern.
	sta	PORTB	; 8D 00 60	; Write to data port B (PORTB).
	lda	#$aa	; A9 AA		; Even-bits pattern.
	sta	PORTB	; 8D 00 60	; Write to data port B (PORTB).	
	jmp Loop	; 4C 05 80	; Repeat indefinitely by jumping back to $8005.
	
	org	$FFFC
	word $Reset	; Reset vector (FFFC, FFFD) is set to location $8000.
	word $0000	; Fill 32K to end.