Multiple driver error

[madalin1990]

I can't find the source of this error:
"Signal int_sum[0][0] in unit multiplier is connected to following multiple drivers:"

Here's the code:

module multiplier(A ,B , P);

parameter BIT_WIDTH = 4;

input [BIT_WIDTH-1 : 0] A;
input [BIT_WIDTH-1 : 0] B;
output  [2*BIT_WIDTH-1 : 0] P;

wire [BIT_WIDTH-1 : 0] int_sum  [BIT_WIDTH-1 : 0];
wire [BIT_WIDTH-1 : 0] int_cout [BIT_WIDTH-1 : 0];

genvar i,j;
generate
   for(i=0;i<=BIT_WIDTH-1;i=i+1)				// B corresponds to i
		for(j=0;j<=BIT_WIDTH-1;j=j+1)			// A corespond to j
			if(i==0)
				if(j <= BIT_WIDTH-1 )
					begin:FIRST_ROW
							mul_unit(
								.in_x(A[j]), 
								.in_y(B[0]), 
								.cin(), 
								.sin(), 
								.cout(int_cout[i][0]), 
								.sout(int_sum[i][0])
										);
					end
			
			else
					if(i == BIT_WIDTH-1)
						begin:LAST_ROW
								mul_unit(
									.in_x(), 
									.in_y(B[i]), 
									.cin(int_cout[i-1][j]), 
									.sin(int_sum[i-1][j+1]), 
									.cout(int_cout[i][j]), 
									.sout(int_sum[i][j])
											);
						end
					else
							begin:OTHER_ROW
							mul_unit(
								.in_x(), 
								.in_y(B[i]), 
								.cin(int_cout[i-1][j]), 
								.sin(int_sum[i-1][j+1]), 
								.cout(int_cout[i][j]), 
								.sout(int_sum[i][j])
								);
							end
endgenerate;

	for(i=0;i<=BIT_WIDTH-1;i=i+1)			// B corresponds to i
		for(j=0;j<=BIT_WIDTH-1;j=j+1)		// A corespond to j
			if(i< BIT_WIDTH -1 )
				assign P[i] = int_sum[i][0]	;
			else
				if(j< BIT_WIDTH-1)
					assign P[BIT_WIDTH+j] = int_sum[i][j];
				else
					assign P[BIT_WIDTH+j] = int_cout[i][j]; 
		

endmodule

 

[TrickyDicky]

You didnt list the multiple drivers...

 

[kornukhin]

Probably, because 'else' at line 29 corresponds to 'if' at line 17 (not 16).
Use additional begin-end for each if-else.

 

[mrflibble]

Now while i^2 = j^2, i != j.

I think you may have put an i where you intended a j.

This bit

generate
   for(i=0;i<=BIT_WIDTH-1;i=i+1)				// B corresponds to i
		for(j=0;j<=BIT_WIDTH-1;j=j+1)			// A corespond to j
			if(i==0)
				if(j <= BIT_WIDTH-1 ) // <== are you sure about this? (*)
					begin:FIRST_ROW
							mul_unit(
								.in_x(A[j]), 
								.in_y(B[0]), 
								.cin(), 
								.sin(), 
								.cout(int_cout[i][0]), 
								.sout(int_sum[i][0]) // <== That one!
										);

First iteration, i=0. And j will iterate over 0 to BIT_WIDTH-1. for j=0 everything is fine (no conflict). And the next round j = 1 ... Then you still have i=0, so you try to assign the .sout of your mul_unit twice to int_sum[0][0]. And same for j=2 etc etc.

The thing marked "are you sure about this" ... how is that statement ever NOT going to be true in that loop? So what are the "else" statements after it going to do?

 

[madalin1990]

"You didnt list the multiple drivers..." ---- Well this is the message xilinx ise webpack returned

As always you're right mr.flibble, that line is useless.regarding the error I think i solved it.I have tangled i with j in several places

 

[mrflibble]

Yeah, mixing up your loop variables is always a fun way to generate some head scratching moments. Anyways, glad you managed to solve it.