HexToDecimal.8

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Celius wrote 8-, 16-, and 24-bit binary to decimal converters. They work by storing the BCD version of 1, 2, 4, 8, 16, ..., 32768, adding them all up digit-wise, and performing the carry through big lookup tables.

<source lang="6502"> HexToDecimal.8:

Given
Hex value in Hex0
Returns decimal value in DecOnes, DecTens, and DecHundreds.

lda #$00 sta DecOnes sta DecTens sta DecHundreds

lda Hex0 and #$0F tax lda HexDigit00Table,x sta DecOnes lda HexDigit01Table,x sta DecTens

lda Hex0 lsr a lsr a lsr a lsr a tax lda HexDigit10Table,x clc adc DecOnes sta DecOnes lda HexDigit11Table,x adc DecTens sta DecTens lda HexDigit12Table,x sta DecHundreds

clc ldx DecOnes lda DecimalSumsLow,x sta DecOnes


lda DecimalSumsHigh,x adc DecTens tax lda DecimalSumsLow,x sta DecTens

lda DecimalSumsHigh,x adc DecHundreds tax lda DecimalSumsLow,x sta DecHundreds ;118

rts

HexToDecimal.16:

Given
Hex value in Hex0 and Hex1.
Returns decimal value in DecOnes, DecTens, DecHundreds, DecThousands, DecTenThousands.

lda #$00 sta DecOnes sta DecTens sta DecHundreds sta DecThousands sta DecTenThousands

lda Hex0 and #$0F tax lda HexDigit00Table,x sta DecOnes lda HexDigit01Table,x sta DecTens

lda Hex0 lsr a lsr a lsr a lsr a tax lda HexDigit10Table,x clc adc DecOnes sta DecOnes lda HexDigit11Table,x adc DecTens sta DecTens lda HexDigit12Table,x sta DecHundreds

lda Hex1 and #$0F tax lda HexDigit20Table,x clc adc DecOnes sta DecOnes lda HexDigit21Table,x adc DecTens sta DecTens lda HexDigit22Table,x adc DecHundreds sta DecHundreds lda HexDigit23Table,x sta DecThousands

lda Hex1 lsr a lsr a lsr a lsr a tax clc lda HexDigit30Table,x adc DecOnes sta DecOnes lda HexDigit31Table,x adc DecTens sta DecTens lda HexDigit32Table,x adc DecHundreds sta DecHundreds lda HexDigit33Table,x adc DecThousands sta DecThousands lda HexDigit34Table,x sta DecTenThousands

clc ldx DecOnes lda DecimalSumsLow,x sta DecOnes


lda DecimalSumsHigh,x adc DecTens tax lda DecimalSumsLow,x sta DecTens

lda DecimalSumsHigh,x adc DecHundreds tax lda DecimalSumsLow,x sta DecHundreds

lda DecimalSumsHigh,x adc DecThousands tax lda DecimalSumsLow,x sta DecThousands

lda DecimalSumsHigh,x adc DecTenThousands tax lda DecimalSumsLow,x sta DecTenThousands ;263

rts


HexToDecimal.24:

Given hex value in Hex0, Hex1, and Hex2
Returns decimal value in DecOnes, DecTens, DecHundreds, DecThousands, DecTenThousands, DecHundredThousands, DecMillions,
and DecTenMillions.

lda #$00 sta DecOnes sta DecTens sta DecHundreds sta DecThousands sta DecTenThousands sta DecHundredThousands sta DecMillions sta DecTenMillions


lda Hex0 and #$0F tax lda HexDigit00Table,x sta DecOnes lda HexDigit01Table,x sta DecTens

lda Hex0 lsr a lsr a lsr a lsr a tax lda HexDigit10Table,x clc adc DecOnes sta DecOnes lda HexDigit11Table,x adc DecTens sta DecTens lda HexDigit12Table,x sta DecHundreds


lda Hex1 and #$0F tax lda HexDigit20Table,x clc adc DecOnes sta DecOnes lda HexDigit21Table,x adc DecTens sta DecTens lda HexDigit22Table,x adc DecHundreds sta DecHundreds lda HexDigit23Table,x sta DecThousands


lda Hex1 lsr a lsr a lsr a lsr a tax clc lda HexDigit30Table,x adc DecOnes sta DecOnes lda HexDigit31Table,x adc DecTens sta DecTens lda HexDigit32Table,x adc DecHundreds sta DecHundreds lda HexDigit33Table,x adc DecThousands sta DecThousands lda HexDigit34Table,x sta DecTenThousands

lda Hex2 and #$0F tax clc lda HexDigit40Table,x adc DecOnes sta DecOnes lda HexDigit41Table,x adc DecTens sta DecTens lda HexDigit42Table,x adc DecHundreds sta DecHundreds lda HexDigit43Table,x adc DecThousands sta DecThousands lda HexDigit44Table,x adc DecTenThousands sta DecTenThousands lda HexDigit45Table,x sta DecHundredThousands

lda Hex2 lsr a lsr a lsr a lsr a tax clc lda HexDigit50Table,x adc DecOnes sta DecOnes lda HexDigit51Table,x adc DecTens sta DecTens lda HexDigit52Table,x adc DecHundreds sta DecHundreds lda HexDigit53Table,x adc DecThousands sta DecThousands lda HexDigit54Table,x adc DecTenThousands sta DecTenThousands lda HexDigit55Table,x adc DecHundredThousands sta DecHundredThousands lda HexDigit56Table,x sta DecMillions lda HexDigit57Table,x sta DecTenMillions

clc ldx DecOnes lda DecimalSumsLow,x sta DecOnes


lda DecimalSumsHigh,x adc DecTens tax lda DecimalSumsLow,x sta DecTens

lda DecimalSumsHigh,x adc DecHundreds tax lda DecimalSumsLow,x sta DecHundreds

lda DecimalSumsHigh,x adc DecThousands tax lda DecimalSumsLow,x sta DecThousands

lda DecimalSumsHigh,x adc DecTenThousands tax lda DecimalSumsLow,x sta DecTenThousands

lda DecimalSumsHigh,x adc DecHundredThousands tax lda DecimalSumsLow,x sta DecHundredThousands

lda DecimalSumsHigh,x adc DecMillions tax lda DecimalSumsLow,x sta DecMillions

lda DecimalSumsHigh,x adc DecTenMillions tax lda DecimalSumsLow,x sta DecTenMillions

;475

rts

                        • Pre-Converted Hex to Decimal Tables *************
1 byte

HexDigit32Table: .db $0

HexDigit00Table: HexDigit56Table: DecimalSumsLow:

55 bytes

.db $0,$1,$2,$3,$4,$5,$6,$7,$8,$9,$0,$1,$2,$3,$4,$5 .db $6,$7,$8,$9,$0,$1,$2,$3,$4,$5,$6,$7,$8,$9,$0,$1 .db $2,$3,$4,$5,$6,$7,$8,$9,$0,$1,$2,$3,$4,$5,$6,$7 .db $8,$9,$0,$1,$2,$3,$4

HexDigit01Table: HexDigit57Table: DecimalSumsHigh:

55 bytes

.db $0,$0,$0,$0,$0,$0,$0,$0,$0,$0,$1,$1,$1,$1,$1,$1 .db $1,$1,$1,$1,$2,$2,$2,$2,$2,$2,$2,$2,$2,$2,$3,$3 .db $3,$3,$3,$3,$3,$3,$3,$3,$4,$4,$4,$4,$4,$4,$4,$4 .db $4,$4,$5,$5,$5,$5,$5

111 bytes

HexDigit50Table: HexDigit40Table: HexDigit30Table: HexDigit20Table: HexDigit10Table: .db $0,$6,$2,$8,$4,$0,$6,$2,$8,$4,$0,$6,$2,$8,$4,$0

HexDigit11Table: .db $0,$1,$3,$4,$6,$8,$9,$1,$2,$4,$6,$7,$9,$0,$2,$4

HexDigit12Table: .db $0,$0,$0,$0,$0,$0,$0,$1,$1,$1,$1,$1,$1,$2,$2,$2

HexDigit21Table: .db $0,$5,$1,$6,$2,$8,$3,$9,$4,$0,$6,$1,$7,$2,$8,$4

HexDigit22Table: .db $0,$2,$5,$7,$0,$2,$5,$7,$0,$3,$5,$8,$0,$3,$5,$8

HexDigit23Table: .db $0,$0,$0,$0,$1,$1,$1,$1,$2,$2,$2,$2,$3,$3,$3,$3

HexDigit31Table: .db $0,$9,$9,$8,$8,$8,$7,$7,$6,$6,$6,$5,$5,$4,$4,$4

HexDigit33Table: .db $0,$4,$8,$2,$6,$0,$4,$8,$2,$6,$0,$5,$9,$3,$7,$1

HexDigit34Table: .db $0,$0,$0,$1,$1,$2,$2,$2,$3,$3,$4,$4,$4,$5,$5,$6

HexDigit41Table: .db $0,$3,$7,$0,$4,$8,$1,$5,$8,$2,$6,$9,$3,$6,$0,$4

HexDigit42Table: .db $0,$5,$0,$6,$1,$6,$2,$7,$2,$8,$3,$8,$4,$9,$5,$0

HexDigit43Table: .db $0,$5,$1,$6,$2,$7,$3,$8,$4,$9,$5,$0,$6,$1,$7,$3

HexDigit44Table: .db $0,$6,$3,$9,$6,$2,$9,$5,$2,$8,$5,$2,$8,$5,$1,$8

HexDigit45Table: .db $0,$0,$1,$1,$2,$3,$3,$4,$5,$5,$6,$7,$7,$8,$9,$9

HexDigit51Table: .db $0,$7,$5,$2,$0,$8,$5,$3,$0,$8,$6,$3,$1,$8,$6,$4

HexDigit52Table: .db $0,$5,$1,$7,$3,$8,$4,$0,$6,$1,$7,$3,$9,$4,$0,$6

HexDigit53Table: .db $0,$8,$7,$5,$4,$2,$1,$0,$8,$7,$5,$4,$2,$1,$0,$8

HexDigit54Table: .db $0,$4,$9,$4,$9,$4,$9,$4,$8,$3,$8,$3,$8,$3,$8,$2

HexDigit55Table: .db $0,$0,$0,$1,$1,$2,$2,$3,$3,$4,$4,$5,$5,$6,$6,$7 </source>

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