Stewpit Indy questions <:-/

der Mouse wrote: The beauty of the Hamming codes was the simplicity of doing so. If you have D data bits, you take build an L-row matrix wherein each column is the L-bit representation of such that no two columns are the same -- and the "0...0" vector never appears (L is the number of bits that you are adding to the data bits -- there must be D+L columns in said matrix). So, for an 8 bit value, you would create a matrix: 0 0 0 0 0 0 0 1 1 1 1 1 0 0 0 1 1 1 1 0 0 0 0 1 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 Your input code word (D+C digits... C=4 here) is then multiplied by this matrix. A result of "0..0" indicates a valid code word (no error). Any other value tells you which bit needs to be twiddled in the input code word. The "check digits" (given this form of the code) are interspersed among the data digits by noting where the column vectors in this matrix have only a single bit set in them. (E.g. the 1st, 2nd, 4th and 8th columns). You can obviously rearrange the columns. Or, select a different subset of those available (e.g., replace the last column with 1 1 1 1) [let me know if this isn't quite right... I'm just calling it up from memory and I haven't had to design any ECC hardware in *decades*! :-/ ]