Difference between revisions of "Converting Binary Coded Decimal"
(Added 6502 code.) |
m |
||
| Line 8: | Line 8: | ||
A 7-bit binary number can be converted to BCD so it can be printed in hex with the following 6502 code: | A 7-bit binary number can be converted to BCD so it can be printed in hex with the following 6502 code: | ||
| − | \ | + | \ Convert binary number to BCD |
| − | \ | + | \ ---------------------------- |
| − | \ On entry, A=value | + | \ On entry, A=value 0-99 |
| − | \ On exit, A | + | \ On exit, A=BCD value |
| + | \ X corrupted | ||
.BINtoBCD | .BINtoBCD | ||
TAX :\ Transfer number to X | TAX :\ Transfer number to X | ||
Revision as of 01:20, 3 October 2016
Binary Coded Decimal (BCD) is a method of representing a decimal number as a hexadecimal value using the hex digits 0-9 and ignoring A-F. For example, the number 21 (hex &15) would be represented as &21 (decimal 33). It can be a convenient internal representation of decimal numbers as each hexadecimal digit can be displayed without any further processing. See Wikipedia. BCD values can be decoded with:
number% = VALSTR$~bcd%
Numbers can be encoded in BCD using:
bcd% = EVAL("&"+STR$number%)
A 7-bit binary number can be converted to BCD so it can be printed in hex with the following 6502 code:
\ Convert binary number to BCD \ ---------------------------- \ On entry, A=value 0-99 \ On exit, A=BCD value \ X corrupted .BINtoBCD TAX :\ Transfer number to X LDA #&99 :\ Start with -1 in BCD form SED :\ Switch to Decimal arithmetic .PrDecLp CLC:ADC #1 :\ Add 1 with BCD arithmetic DEX:BPL PrDecLp :\ Add 1 for the total in X until X<0 CLD:RTS :\ Switch back to Binary arithmetic
Jgharston 21:11, 23 June 2007 (BST)
Jgharston (talk) 00:19, 3 October 2016 (UTC)
