Codebase64 wiki

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:

start:
		lda #$30	// clear the result buffer
		ldy #$00
	clear:
		sta result,y
		iny
		cpy #$05
		bne 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 alread haven
		cmp #$3a	// passing 10 with the addition?
		bcc notten
		sbc #$0a	// if so, subtract 10 
notten:
		sta result,y
zero:
		dex
		dey
		bpl loop2	// loop until all 5 digits have been
		jmp loop1
table:
		.byte 0,0,0,0,1
		.byte 0,0,0,0,2
		.byte 0,0,0,0,4
		.byte 0,0,0,0,8
		.byte 0,0,0,1,6
		.byte 0,0,0,3,2
		.byte 0,0,0,6,4
		.byte 0,0,1,2,8
		.byte 0,0,2,5,6
		.byte 0,0,5,1,2
		.byte 0,1,0,2,4
		.byte 0,2,0,4,8
		.byte 0,4,0,9,6
		.byte 0,8,1,9,2
		.byte 1,6,3,8,4
		.byte 3,2,7,6,8

result:
		.byte 0,0,0,0,0
lobyte:
		.byte 11
hibyte:
		.byte 0