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NAME

       lut5 - Arbitrary 5-input logic function based on a look-up table

SYNOPSIS

       loadrt lut5 [count=N|names=name1[,name2...]]

DESCRIPTION

       lut5 constructs a logic function with up to 5 inputs using a look-up table.  The value for
       function can be determined by writing the truth table, and computing the sum  of  all  the
       weights for which the output value would be TRUE.  The weights are hexadecimal not decimal
       so hexadecimal math must be used to sum the weights.  A wiki  page  has  a  calculator  to
       assist in computing the proper value for function.

       https://wiki.linuxcnc.org/cgi-bin/wiki.pl?Lut5

       Note  that  LUT5  will  generate any of the 4,294,967,296 logical functions of 5 inputs so
       AND, OR, NAND, NOR, XOR and every other combinatorial function is possible.

   Example Functions
       A 5-input and function is TRUE only when all the inputs are true, so the correct value for
       function is 0x80000000.

       A  2-input  or  function  would  be  the  sum of 0x2 + 0x4 + 0x8, so the correct value for
       function is 0xe.

       A 5-input or function is TRUE whenever any of the inputs are true, so  the  correct  value
       for  function  is  0xfffffffe. Because every weight except 0x1 is true the function is the
       sum of every line except the first one.

       A 2-input xor function is TRUE whenever exactly one of the inputs is true, so the  correct
       value  for function is 0x6.  Only in-0 and in-1 should be connected to signals, because if
       any other bit is TRUE then the output will be FALSE.

       ┌───────────────────────────────────────────────────┐
       │       Weights for each line of truth table        │
       ├──────────────────────────────────────┬────────────┤
       │Bit 4   Bit 3   Bit 2   Bit 1   Bit 0Weight   │
       ├──────────────────────────────────────┼────────────┤
       │  0       0       0       0       0   │        0x1 │
       │  0       0       0       0       1   │        0x2 │
       │  0       0       0       1       0   │        0x4 │
       │  0       0       0       1       1   │        0x8 │
       │  0       0       1       0       0   │       0x10 │
       │  0       0       1       0       1   │       0x20 │
       │  0       0       1       1       0   │       0x40 │
       │  0       0       1       1       1   │       0x80 │
       │  0       1       0       0       0   │      0x100 │
       │  0       1       0       0       1   │      0x200 │
       │  0       1       0       1       0   │      0x400 │
       │  0       1       0       1       1   │      0x800 │
       │  0       1       1       0       0   │     0x1000 │
       │  0       1       1       0       1   │     0x2000 │
       │  0       1       1       1       0   │     0x4000 │
       │  0       1       1       1       1   │     0x8000 │
       │  1       0       0       0       0   │    0x10000 │
       │  1       0       0       0       1   │    0x20000 │
       │  1       0       0       1       0   │    0x40000 │
       │  1       0       0       1       1   │    0x80000 │
       │  1       0       1       0       0   │   0x100000 │
       │  1       0       1       0       1   │   0x200000 │
       │  1       0       1       1       0   │   0x400000 │
       │  1       0       1       1       1   │   0x800000 │
       │  1       1       0       0       0   │  0x1000000 │
       │  1       1       0       0       1   │  0x2000000 │
       │  1       1       0       1       0   │  0x4000000 │
       │  1       1       0       1       1   │  0x8000000 │
       │  1       1       1       0       0   │ 0x10000000 │
       │  1       1       1       0       1   │ 0x20000000 │
       │  1       1       1       1       0   │ 0x40000000 │
       │  1       1       1       1       1   │ 0x80000000 │
       └──────────────────────────────────────┴────────────┘

FUNCTIONS

       lut5.N

PINS

       lut5.N.in-0 bit in
       lut5.N.in-1 bit in
       lut5.N.in-2 bit in
       lut5.N.in-3 bit in
       lut5.N.in-4 bit in
       lut5.N.out bit out

PARAMETERS

       lut5.N.function u32 rw

SEE ALSO

       and(9), logic(9), not(9), or2(9), xor2(9).

AUTHOR

       Jeff Epler

LICENSE

       GPL