counter-frag-2.s

nmi_vec
	pha
	bit via1_t1c_l	; read anything from t1c_l
			; to turn off interrupt signal
	lda char_to_via1; a = char_to_via2
	sta via1_iora	; send to via2 port A
	clc
	rol		; a =<< 1
	bne ++		; if a == 0 then
	lda #$1		;   a = 1
++
	sta char_to_via2; char_to_via = a
+
	pla
	rti


irq_vec
	pha
	bit via2_t1c_l	; read anything from t1c_l
			; to turn off interrupt signal
	lda delay_via	; a = delay_via
	bne +		; if a == 0 then 
	lda #$10	;   a = $10
+
	sec
	sbc #1		; a--
	sta delay_via	; delay_via = a
	bne +		; 

	lda char_to_via2; a = char_to_via
	sta via2_iora	; send to via2 port A
	clc
	rol		; a =<< 1
	bne ++		; if a == 0 then
	lda #$1		;   a = 1
++
	sta char_to_via2; char_to_via = a
+
	pla
	rti