Verilog 2's Complement Shifter


D

Davy

Hi all,

I am new to Verilog and want to build a 2's Complement Shifter.

I found
%displayb(8'b0001_1000>>2); //Output 0000_0110
%displayb(8'b1001_1000>>2); //Output 0010_0110

So >> is unsigned shift.
How can I build a signed (2's Complement) shift based on >>?
i.e. I want 8'b1001_1000>>2 //Output 1110_0110

Any suggestions will be appreciated!
Best regards,
Davy
 
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S

Spehro Pefhany

Hi all,

I am new to Verilog and want to build a 2's Complement Shifter.

I found
%displayb(8'b0001_1000>>2); //Output 0000_0110
%displayb(8'b1001_1000>>2); //Output 0010_0110

So >> is unsigned shift.
How can I build a signed (2's Complement) shift based on >>?
i.e. I want 8'b1001_1000>>2 //Output 1110_0110

Any suggestions will be appreciated!
Best regards,
Davy

Verilog 2001 has >>> (signed shift operator)


Best regards,
Spehro Pefhany
 
A

Alan Nishioka

Davy said:
How can I build a signed (2's Complement) shift based on >>?
i.e. I want 8'b1001_1000>>2 //Output 1110_0110

How about
12'b1111_1001_1000>>2
or
{ 32{b[7]}, b } >> 2
 
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S

sharp

But note that the so-called "signed shift" only gives you a signed or
arithmetic shift if it is used in a signed expression. In an unsigned
expression, you get an unsigned or logical shift. It isn't really a
"signed shift". It is a "shift using the signedness of the
expression". It is what the ordinary shift operator should have been
in the first place.
 

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