Cryptographic applications commonly require circular shifts. Whereas these shifts can be accomplished using a shift register, combinational shifting is required to complete these operations in a reasonable amount of time. Design an 8 bit barrel shifter that has 8 data inputs and 8 data outputs, and 3 control inputs that determine the shift amount (0-7). An additional enable input controls whether the outputs are tri-state or not. Use the truth table below as the functionality and use the entity declaration given.
en s2 s1 s0 c7 c6 c5 c4 c3 c2 c1 c0
0 0 0 0
a7 a6 a5 a4 a3 a2 a1 a0
0 0 0 1
a0 a7 a6 a5 a4 a3 a2 a1
0 0 1 0
a1 a0 a7 a6 a5 a4 a3 a2
0 0 1 1
a2 a1 a0 a7 a6 a5 a4 a3
0 1 0 0
a3 a2 a1 a0 a7 a6 a5 a4
0 1 0 1
a4 a3 a2 a1 a0 a7 a6 a5
0 1 1 0
a5 a4 a3 a2 a1 a0 a7 a6
0 1 1 1
a6 a5 a4 a3 a2 a1 a0 a7
1 0 0 0
Z Z Z Z Z Z Z Z
1 0 0 1
Z Z Z Z Z Z Z Z
1 0 1 0
Z Z Z Z Z Z Z Z
1 0 1 1
Z Z Z Z Z Z Z Z
1 1 0 0
Z Z Z Z Z Z Z Z
1 1 0 1
Z Z Z Z Z Z Z Z
1 1 1 0
Z Z Z Z Z Z Z Z
1 1 1 1
Z Z Z Z Z Z Z Z
Use the following entity
entity barrel is
port (a : in std_logic_vector (7 downto 0); s : in std_logic (2 downto 0; en : in std_logic;
c : out std_logic_vector (7 downto 0)); end entity barrel;
Develop a behavioral architecture for the system.
Perform the following steps
a. Modify the test bench given in homework #1 to test this circuit.
b. Compile all of the files
c. Simulate to verify correctness.
Turn in all VHDL files.
