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[SOLVED] Any Shortcut for assigning msb of a product to a variable

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rahdirs

rahdirs

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Hi,

I am multiplying two variables (16 bit) in verilog, so the maximum number of bits of the product is 32 bits. Is there any shortcut to assign the msb 16 bits to a variable ?

Code: 
	parameter a = 16'hABCD;
	parameter b = 16'hFFFF;
	wire [15:0] c;

	assign c = a*b;

c will be assigned the 16 lsb bits, is there any shorter way of doing this without declaring a 32 bit variable as in,

Code: 
        wire [31:0] product
	wire [15:0] c;

	assign product = a*b;
        assign c = product[31:16]
 

untested but the following might work:
Code Verilog - [expand]
1

assign c = (a*b) >> 16;


the >> will be performed prior to the assignment.
 

I can test this tomorrow when I'm sitting at my desk but you might be able to do this:

Code: 
assign c = 16'(32'(a*b)[31:16]);

I am unsure why you need to avoid two extra lines to accomplish this? I don't know if the above will synthesize.
 

Hi,

Are the input values "signed" or "unsigned"?

Klaus
 

In SystemVerilog, you can do select of a concatenation:

Code: 
assign c = {a*b}[31:16];
 

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