AR# 4348


M1.5: EPIC: How to read the equation inside of a LUT in FPGAs



Equations, LUT, FPGAs



General Description:

Customers sometimes wonder how the logic was synthesized into Look

Up Tables in FPGAs.


Equations are generated in the form of report files for CPLDs (such as

XC9500 family) only . For FPGAs, where the Combinational logic is

implemented as LUT (look up table) , you can look up what is in a LUT

in EPIC design editor (lowest button on the right side in Design Manager

GUI). Alternatively, you can run 'ncdread' in command line (Dos

prompt) on the map.ncd file or design.ncd file.

To look at the equation in EPIC Design Editor:

1. In EPIC Design Editor, select the CLB of your choice. The color

of the CLB will change to red.

2. Click 'editblock' button on the right. It will bring you to the logic

block editor.

3. Click on 'Attr' button in Logic Block Editor. That will bring up the

'logic equations' window.

4. You can edit the equation there if you like.

To run 'ncdread' in command line, do the followings:

1. Open a dos prompt.

2. Go to project director\xproj\<ver>\<rev> directory.

3. Run

Ncdread -o <output_dump_file> map.ncd

4. Open the <output_dump_file> with any text editor.

(Note: In order to be able to run the command line, you may need to

type: set path= %xilinx%\bin\nt and enter at the command prompt

before step 3.

For more information, please refer to Libraries Guides from the

dynatext browser. (Click on Start-> Programs -> Xilinx

Foundations Series -> Online Books to invoke the dynatext browser
AR# 4348
Date 11/14/2011
Status Archive
Type General Article
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