Double Precision Binary to BCD Conversion
tomcrawford
Posts: 1,129
in Propeller 1
I couldn't find extended precision binary-to-BCD conversion in spin, so here one is. It does up to (2^64)-1. You give it two longs and it return 20 bytes of BCD. I checked it against all 64 powers of two, which it got correct. The method is discussed in the comment section of the code, but basically it repeatedly subtracts powers of 10.
Comments
16-bit example: BCD_value Hex_value Start 0000_0000 0000_0000|0000_0100 1101_0010 1234 = $04D2 1 Shift left |0000_1001 1010_010 2 Shift left |0001_0011 0100_10 3 Shift left |0010_0110 1001_0 4 Shift left |0100_1101 0010 5 Shift left |1001_1010 010 6 Shift left 1|0011_0100 10 7 Shift left 10|0110_1001 0 8 Shift left 100|1101_0010 9 Shift left 1001|1010_010 Add 3 to 1st nibble (>4) 1100|1010_010 10 Shift left 1_1001|0100_10 Add 3 to 1st nibble 1_1100|0100_10 11 Shift left 11_1000|1001_0 Add 3 to 1st nibble 11_1011|1001_0 12 Shift left 111_0111|0010 Add 3 to 2nd nibble 1010_0111|0010 Add 3 to 1st nibble 1010_1010|0010 13 Shift left 1 0101_0100|010 Add 3 to 2nd nibble 1 1000_0100|010 14 Shift left 11 0000_1000|10 Add 3 to 1st nibble 11 0000_1011|10 15 Shift left 110 0001_0111|0 Add 3 to 3rd nibble 1001 0001_0111|0 Add 3 to 1st nibble 1001 0001_1010|0 16 Shift left 1_0010 0011_0100| = $1234Attached 64-bit Spin and PASM routines.