lut5 - Arbitrary 5-input logic function based on a look-up table
loadrt
lut5 [count=
N|names=name1[,name2...]]
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.
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 0 |
Weight |
|
| 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 |
-
lut5.N
-
- 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
- lut5.N.function u32 rw
and(9),
logic(9),
not(9),
or2(9),
xor2(9).
Jeff Epler
GPL