xilinx constraint declaration need help !

Matrix_YL · Dec 9, 2005

xilinx multiplier synthesis block vs lut

Hi all

I spend too much block multiplier on my design ,so I want to use some of them by lut .

I do my constraint according to xilinx cdg.pdf .

Specify as follows:
// synthesis attribute mult_style [of] {module_name|signal_name} [is]
{auto|block|lut|pipe_lut|pipe_block|CSD|KCM};

module multiplier(
//Output
result_1,result_2,
//Input
a,b,c,d
);

input[3:0] a;
input[3:0] b;
input[3:0] c;
input[3:0] d;
output[7:0] result_1;
output[7:0] result_2;

assign result_1= a*b; // synthesis attribute mult_style of {result_1} is {lut};

assign result_2= c*d; // synthesis attribute mult_style of {result_2} is {block};
endmodule

but the synthesized report generated by two block multiplier

=============================================================
* HDL Analysis *
=========================================================================
Analyzing top module <multiplier>.
Module <multiplier> is correct for synthesis.

"multiplier.v" line 36: Cannot find <{result_1}> in module <multiplier>, property <mult_style> with Value <{lut}> is ignored.
"multiplier.v" line 38: Cannot find <{result_2}> in module <multiplier>, property <mult_style> with Value <{block}> is ignored.
Set property "resynthesize = true" for unit <multiplier>.

what's wrong with my HDL ? or Mybe I misunderstand the usage of xilinx constraint declaration .can you help me solve this problem ?
thank you very much !

tkbits · Dec 9, 2005

set as top module xilinx

Remove the {} ?
So it looks like

Code:

// synthesis attribute mult_style of result_1 is lut;

{} is typically used to group choices together in a syntax description.

Matrix_YL · Dec 10, 2005

google groups mult_style

Hi tkbits
I do it according to what you indicated,but fail to implement!

[/
HDL Analysis *
=========================================================================
Analyzing top module <multiplier>.
Module <multiplier> is correct for synthesis.

"multiplier.v" line 36: Cannot find <{result_1}> in module <multiplier>, property <mult_style> with Value <lut> is ignored.
"multiplier.v" line 38: Cannot find <{result_2}> in module <multiplier>, property <mult_style> with Value <block> is ignored.
Set property "resynthesize = true" for unit <multiplier>.

echo47 · Dec 10, 2005

cdg.pdf xilinx

tkbits instructions are correct. You didn't remove all the {}.
Here is a working module:

Code:

module multiplier (result_1, result_2, a, b, c, d);
  input  [3:0] a, b, c, d;
  output [7:0] result_1, result_2;

  assign result_1 = a * b; // synthesis attribute mult_style of result_1 is lut;
  assign result_2 = c * d; // synthesis attribute mult_style of result_2 is block;
endmodule

Matrix_YL · Dec 10, 2005

assign synthesis to lut

Hi tkbits
I do it according to what you indicated,but fail to implement!

It's my mistake.

thanks for your help

xilinx constraint declaration need help !

Matrix_YL

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