FR3TO1.Text

Lisa · TEXT

Filename	`FR3TO1.Text`
Size	0.00 MB
Subsection	firmware / ROM88
Downloads	2

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Contents

.Page
;++
;		FR3TO1 will take three bytes and create one composite byte from them.
;
;		Input register usage:
;			A :=	>CCCCCCCC<
;			X :=	>BBBBBBBB<
;			Y :=	>AAAAAAAA<
;
;		Output register usage:
;			A :=	>00AABBCC< == Nibblized
;--

FR3TO1	.Equ *			; From three to one routine
	Lsr	A		; Ignore low six bits of "A" as they
	Lsa	A		;  will get shifted out and lost
	Sta	Temp1		; >00CCxxxx<
	Txa
	And	#0C0		; Clear low bits
	Ora	Temp1		; >BBCCxxxx<
	Lsr	A
	Lsr	A
	Sta	Temp1		; >00BBCCxx<
	Tya
	And	#0C0		; Clear low bits
	Ora	Temp!		; >AABBCCxx<
	Lsr	A
	Lsr	A		; >00AABBCC<
	Tax
	Lda	Nibl,X		; Nibblize the new composite byte
	Rts