11.2.3.8 Shift Operators

Shift operators shift data left or right by a specified number of bits. The following examples infer left and right shift operators.

VHDL
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;
use IEEE.std_logic_unsigned.all;
entity shift is
port (data : in std_logic_vector(3 downto 0);
q1, q2 : out std_logic_vector(3 downto 0));
end shift;
architecture rtl of shift is
begin
process (data)
begin
q1 <= shl (data, "10"); -- logical shift left
q2 <= shr (data, "10"); --logical shift right
end process;
end rtl;

or

library IEEE;
use IEEE.std_logic_1164.all;
entity shift is
port (data : in std_logic_vector(3 downto 0);
q1, q2 : out std_logic_vector(3 downto 0));
end shift;
architecture rtl of shift is
begin
process (data)
begin
q1 <= data(1 downto 0) & “10”; -- logical shift left
q2 <= “10” & data(3 downto 2); --logical shift right
end process;
end rtl;
Verilog
module shift (data, q1, q2);
input [3:0] data;
output [3:0] q1, q2;
parameter B = 2;
reg [3:0] q1, q2;
always @ (data)
begin
q1 = data << B; // logical shift left
q2 = data >> B; //logical shift right
end
endmodule