By Mace

This routine converts two bytes decimal to two bytes hexadecimal. 'hiInput' contains hundreds, 'loInput' contains tens and ones, so $0365 equals #365 decimal. It will be converted to 'hiResult' and 'loResult' (in this case $016d, the hexadecimal of 365).

	.pc = $0810

		lda #$00	; Init result bytes
		sta loResult
		sta hiResult
		lda loInput	; Fetch ones and tens
		tax		; Save to X
		and #$0f	; Strip the ones
		tay		; Save to Y
		txa		; Get original ones and tens
		lsr
		lsr
		lsr
		lsr		; Divide by 16 to get tens only
		tax		; Save to X
		tya		; Put the ones in A
		cpx #$00	; No tens? Then skip
		beq PROCEED
		clc
TENS:		adc #$0a	; Add as many tens as value of X
		dex
		bne TENS
PROCEED:	ldx hiInput	; Fetch the hundreds
		beq END		; No hundreds? Then go to end
HUND:		clc
		adc #$64	; Add as many hundreds as value of X
		bcc !+
		inc hiResult	; Increase high byte every passed $FF
!:		dex
		bne HUND
END:		sta loResult	; Store low byte
		rts

hiInput:	.byte $00
loInput:	.byte $01
hiResult:	.byte $00
loResult:	.byte $00