===== Another Hexadecimal to Decimal Conversion =====

by Mace

Garth Wilson used decimal mode in [[Hexadecimal to Decimal Conversion]] and the result was in 3 bytes in decimal mode. I needed plain ASCII, the following routine does just that, using more or less the same method as Garth used:
<code>
start:
		lda #$30	// clear the result buffer
		ldy #$04
	clear:
		sta result,y
		dey
		bcs clear
		ldx #$4f
loop1:
		clc
		rol lobyte
		rol hibyte
		bcs calculate	// when bit drops off, decimal value must be added
				// if not, go to the next bit
		txa
		axs #$05	// ILLEGAL OPCODE, alternatively use lines below
				// sec
				// sbc #$05
				// tax
		bpl loop1
END:
		rts

calculate:
		clc
		ldy #$04
loop2:
		lda table,x	// get decimal equivalent of bit in ASCII numbers
		adc #$00        // add carry, is set if the former addition ≥10
                beq zero	// skip (speed up) when there's nothing to add
		adc result,y	// add to whatever result we already have
		cmp #$3a	// ≥10 with the addition?
		bcc notten      // if not, skip the subtraction
		sbc #$0a	// subtract 10 
notten:
		sta result,y
zero:
		dex
		dey
		bpl loop2	// loop until all 5 digits have been
		jmp loop1
table:                          // decimal values for every bit in 16-bit figure
		.byte 0,0,0,0,1 // %0000000000000001
		.byte 0,0,0,0,2 // %0000000000000010
		.byte 0,0,0,0,4 // %0000000000000100
		.byte 0,0,0,0,8 // %0000000000001000
		.byte 0,0,0,1,6 // %0000000000010000
		.byte 0,0,0,3,2 // %0000000000100000
		.byte 0,0,0,6,4 // %0000000001000000
		.byte 0,0,1,2,8 // %0000000010000000
		.byte 0,0,2,5,6 // %0000000100000000
		.byte 0,0,5,1,2 // %0000001000000000
		.byte 0,1,0,2,4 // %0000010000000000
		.byte 0,2,0,4,8 // %0000100000000000
		.byte 0,4,0,9,6 // %0001000000000000
		.byte 0,8,1,9,2 // %0010000000000000
		.byte 1,6,3,8,4 // %0100000000000000
		.byte 3,2,7,6,8 // %1000000000000000

result:
		.byte 0,0,0,0,0 // this is where the result will be
lobyte:
		.byte $b3       // demonstration value
hibyte:
		.byte $a9       // demonstration value
</code>