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Espresso-mv logic minimization

The multi-value option on the Espresso logic-minimization software can be used to solve the "input-encoding" problem, where you have say some m-bit ROM and some number of outputs n > m, and you want to find out assigning which bit vectors in the ROM to what output vectors will result in the smallest decode logic.

The documentation isn't particularly helpful:

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the closest relevant example I can find is Example 2:

"This example shows a description of a multiple-valued function with 5 binary variables and 3 multiple-valued variables (8 variables total) where the multiple-valued variables have sizes of 4 27 and 10 (note that the last multiple-valued variable is the "output" and also encodes the ON -set, DC -set and OFF -set information)."

.mv 8 5 4 27 10 .ilb in1 in2 in3 in4 in5 .label var=5 part1 part2 part3 part4 .label var=6 a b c d e f g h i j k l m n o p q r s t u v w x y z a1 .label var=7 out1 out2 out3 out4 out5 out6 out7 out8 out9 out10 0-010|1000|100000000000000000000000000|0010000000 10-10|1000|010000000000000000000000000|1000000000 0-111|1000|001000000000000000000000000|0001000000 0-10-|1000|000100000000000000000000000|0001000000 00000|1000|000010000000000000000000000|1000000000 00010|1000|000001000000000000000000000|0010000000 01001|1000|000000100000000000000000000|0000000010 0101-|1000|000000010000000000000000000|0000000000 0-0-0|1000|000000001000000000000000000|1000000000 10000|1000|000000000100000000000000000|0000000000 11100|1000|000000000010000000000000000|0010000000 10-10|1000|000000000001000000000000000|0000000000 11111|1000|000000000000100000000000000|0010000000 . . . 11111|0001|000000000000000000000000001|000000000

For myself I basically just want to find out how to have X bits of external input and Y bits of ROM and optimize the encoding in ROM such that the decode logic is minimized, but I'm struggling to figure out this input file syntax..

Reply to
bitrex
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I figured out how it works, and Espresso-MV only gets you part of the way there for the input-encoding problem, vs just minimizing a Boolean function.

It outputs a set of constraints, where the output decode logic is minimized when an input encoding can be found such that the constraint terms all lie on the faces of a Boolean hypercube.

See e.g. the four-variable problem on the last two pages here:

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and see how the states are encoded such that the path around the square makes it so all the constraint terms have a Hamming distance of one from each other.

Reply to
bitrex

The FPGA tools take your suggestion and map it into their architecture. The days of Karnaugh maps are long gone.

Reply to
John Larkin

Pretty sure the undergrad-textbook Karnaugh maps were always largely pedagogical tool; the digital systems of even the 1950s already needed more complexity than could be easily analyzed graphically.

I suppose someone had to build the Ur-computer without computer-aided design but computers were helping to design computers very early on.

Reply to
bitrex

Incidentally Maurice Karnaugh passed away just last November, at the age of 98

Reply to
bitrex

Karnaugh maps take about 10 minutes to learn from a standing start. I know this because, long ago when I was a second-year undergraduate, I taught everybody in my physics lab section how to do it. (There was a logic minimization segment to the lab assignment.)

It runs out of gas past three or four inputs, but that's plenty for using multifunction gates, for instance.

MFGs are super useful--they're fast, and you can make any two-input logic function from one of two types of three-input gates, so you don't need to keep a whole lot of types.

So every once in awhile I need to use a Karnaugh map, even still.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

"Logic Friday' will jointly minimize up to 16 inputs and outputs, and spit out a gate diagram optimized for either die area or the standard

74xxxxxxxx series ICs.
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It'll also spit out a C function which might occasionally be useful, I think I remember a post one time about someone using one of the really tiny 8-bitters, with like 256 bytes of RAM just to implement a weird logic function.

Reply to
bitrex

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