Difference between revisions of "Converting Binary Coded Decimal"
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'''B'''inary '''C'''oded '''D'''ecimal (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 [http://en.wikipedia.org/wiki/Binary-coded_decimal Wikipedia]. | '''B'''inary '''C'''oded '''D'''ecimal (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 [http://en.wikipedia.org/wiki/Binary-coded_decimal Wikipedia]. | ||
BCD values can be decoded with: | BCD values can be decoded with: | ||
| − | + | number% = VALSTR$~bcd% | |
Numbers can be encoded in BCD using: | Numbers can be encoded in BCD using: | ||
| − | + | bcd% = EVAL("&"+STR$number%) | |
| + | |||
| + | A 7-bit binary number can be converted to BCD so it can be printed in hex with the following 6502 code: | ||
| + | |||
| + | \ Print decimal number by converting it to BCD | ||
| + | \ -------------------------------------------- | ||
| + | \ On entry, A=value to print 0-99 | ||
| + | \ On exit, A,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 | ||
| + | |||
[[User:Jgharston|Jgharston]] 21:11, 23 June 2007 (BST) | [[User:Jgharston|Jgharston]] 21:11, 23 June 2007 (BST) | ||
| + | [[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 00:19, 3 October 2016 (UTC) | ||
Revision as of 02:19, 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:
\ Print decimal number by converting it to BCD \ -------------------------------------------- \ On entry, A=value to print 0-99 \ On exit, A,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)
