CODEWITHSUNDEEP
verilogsystem-verilogvivado
Achyuth SS
Achyuth SS

Reputation: 15

Procedural Assignment not supported in System Verilog

I've written down this following "Design source" code (on Xilinx Vivado) The code is written in System Verilog, and it is the Hamming 7,4 encoder

https://en.wikipedia.org/wiki/Hamming(7,4)


module eccproj(
input logic [3:0] data_in,
output logic [6:0] hamcode);


logic p1,p2,p4;
    
always @(*) begin
p1 = data_in[0] + data_in[1] + data_in[3];
p2 = data_in[0] + data_in[2] + data_in[3];
p4 = data_in[1] + data_in[2] + data_in[3];

// Input : d3 d2 d1    d0
//Output : d7 d6 d5 p4 d3 d2 d1 

assign hamcode = {data_in[3:1] , p4 , data_in[0] , p2 , p1}; // Error on this line

end

endmodule

I am getting error in the line with the comment, and the error reads as follows :

[Synth 8-27] procedural assign not supported

I know that, in Verilog the above assignment works, but how to work it using System Verilog.

It would be great if someone could suggest a way to get rid of the error.

Upvotes: 1

Views: 759

Answers (2)

dave_59
dave_59

Reputation: 42673

You do not need the assign keyword inside a combinational block

module eccproj(
input logic [3:0] data_in,
output logic [6:0] hamcode);


logic p1,p2,p4;
    
always_comb begin
  p1 = data_in[0] + data_in[1] + data_in[3];
  p2 = data_in[0] + data_in[2] + data_in[3];
  p4 = data_in[1] + data_in[2] + data_in[3];

  // Input : d3 d2 d1    d0
  //Output : d7 d6 d5 p4 d3 d2 d1 
  
  hamcode = {data_in[3:1] , p4 , data_in[0] , p2 , p1}; 
end

endmodule

Upvotes: 1

toolic
toolic

Reputation: 62037

It is unusual to use assign within an always block. You likely want to have the assign outside the always block to make your synthesis tool happy.

always @(*) begin
    p1 = data_in[0] + data_in[1] + data_in[3];
    p2 = data_in[0] + data_in[2] + data_in[3];
    p4 = data_in[1] + data_in[2] + data_in[3];

    // Input : d3 d2 d1    d0
    //Output : d7 d6 d5 p4 d3 d2 d1 
end

assign hamcode = {data_in[3:1] , p4 , data_in[0] , p2 , p1};

Upvotes: 2

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