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Visitor
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Registered: ‎04-09-2017

Problem with dff

I tried to implement s27 on virtex-7, in my first code, there was nmos that causes this error:

nmos not supported.

 

module dff (CK,Q,D);
input CK,D;
output Q;
  wire NM, NCK;
  trireg NQ, M;

  nmos N7 (M,D,NCK);
  not P3 (NM,M);
  nmos N9 (NQ,NM,CK);
  not P5 (Q,NQ);
  not P1 (NCK,CK);
endmodule

Then I wrote gate level dff module, but after implement, there were some luts that have feedback (pic 1).

 

blob (1).jpg

pic 1

 

Inline image

after these I wrote behavioral dff code, it works correctly. but it makes some packed cells that contain luts and dff so it will be hard to find next connected cell of other cells (it's back to my Tcl code).

fewf.JPG

 

module dff(
CK
,Q
,D      
    );
    input D, CK ; 
    output Q;
    reg Q;  
    always @ ( posedge CK)begin
      Q <= D;
    end
endmodule

 

 

Is there any way to prevent these problems?

I will be grateful if you answer me, considering that I'm newbie in Vivado.

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