===== 8 bit to hexadecimal conversion =====

by ABujok

This is another way to print a 8 bit integer value as a HEX value on a C64 Screen. The given integer must be loaded into the accu before calling the routine.

<code>
; Example:

	lda #$3F        ; load accu immediate with $3f or 63      
        jsr OUTHEX      ; print $3F
        rts             ; bye

</code>

<code>
; Syntax for DASM

BSOUT  = $ffd2	; Print character in accu

;**************************
; print Akku hex value
;**************************
OUTHEX	tax		; save value for low nibble
	and #$f0	; High nibble
	clc		; clear carry
	ror		; rotate one bit right
	ror		; rotate one bit right
	ror		; rotate one bit right
	ror		; rotate one bit right
	jsr NIB2HEX	; print nibble
	txa		; restore value
	and #$0f	; Low nibble
	jsr NIB2HEX	; print nibble
	rts


;*********************
;* Akku low Nibble to Hex
;*********************
NIB2HEX cmp #$0a	; Accu >= 10?
	bcs HEX		; Yes
DIGIT	clc		; Accu < 10
	adc #$30	; Accu + $30
	jmp OUT		; print
HEX	clc		;
	adc #$37	; Accu + $37
OUT	jmp BSOUT	; Print Accu (HEX nibble) and bye

</code>


Slight optimization:

<code>
;**************************
; print Akku hex value
;**************************
OUTHEX	tax		; save value for low nibble
        lsr             ; ignore CARRY and shift hi nybble to lonybble pos.
	lsr		; 
	lsr		; 
	lsr		; 
	jsr NIB2HEX	; print nibble
	txa		; restore value
	and #$0f	; Low nibble
	jsr NIB2HEX	; print nibble
	rts

;*********************
;* Akku low Nibble to Hex
;*********************
NIB2HEX cmp #$0a	; Accu >= 10?
	bcs HEX		; Yes
        adc #$30	; Accu < 10
	jmp BSOUT       ; Print #$30 - #39
HEX	adc #$36	; Accu >= 10, subtract #$09 to get "A" to "F" (CARRY always set here)
	jmp BSOUT	; Print Accu (HEX nibble) and bye
</code>

Version not using KERNAL:

<code>
    // Dest.          = YREG:XREG
    // Value to utput = ACC
OUTHEX:
    sty $fb
    stx $fc
    ldy #$00
    pha
    lsr
    lsr
    lsr
    lsr
    tax
    lda tab,x
    sta ($fb),y
    iny
    pla
    and #$0f
    tax
    lda tab,x
    sta ($fb),y
    rts

tab:
    .text "0123456789abcdef"
</code>