return signed/unsigned <= shift_right/ shift_left (arg: signed/unsigned; count: natural);
There are two types of shifts:
1- Logical
2- Arithmetic.
A logical shift means that the new bits are replaced with zeros.
An Arithmetic shift means that the replaced bits are substituted in order to maintain the sign of the original number.
* Shift functions are found in numeric_std package file
* Type of shift depends on input to function. Unsigned=Logical, Signed=Arithmetic
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
use IEEE.NUMERIC_STD.ALL;
...
std_logic_vector <=
std_logic_vector(shift_right/shift_left (unsigned/signed (std_logic_vector), to_integer(unsigned(std_logic_vector))));
...
