Project Assignment #6
In this assignment you will be writing yet another alternative architecture for the 8 bit ALU. The
shell for this project step is in pr_step6.vhdl. In this architecture you will be using a package and
modifying the ENTITY of the 8 bit ALU to use a symbolic name for the operation rather than the
P, K, and R binary values. Also, the procedures are moved from being declared in the process to
the package. You will need to add a “USE” statement to the Entity to make the package
procedures visible.
The ENITY will have Pctl, Kctl, and Rctl replaced by alu_op (This is why the declaration is
moved to the package):
ENTITY alt_8bit_alu IS
PORT ( alu_op : IN operations;
A, B : IN BIT_VECTOR ( 7 downto 0);
Cin : IN BIT;
Zout : OUT BIT_VECTOR ( 7 downto 0);
Cout : OUT BIT );
END alt_8bit_alu;
Modify your ARCHITECTURE from step 5 such that the CASE statement uses alu_op to
determine the operation to be performed as illustrated below.
CASE alu_op IS
WHEN op_A => Zout<= A; Cout <= ‘0’;
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WHEN op_negA => neg(A, Ztemp, CoutTemp);
Zout <= Ztemp; Cout <= CoutTemp;
WHEN OTHERS => NULL;
END CASE;
1) First copy the file pr_step6.vhdl. Note that you will need a package. Enter the package
declaration, package body, ALU ENTITY and ALU ARCHITECTURE as noted.
2) Move the procedures that you used for binary addition, 2’s complement, and binary
subtraction to the package. Remember that these are procedure bodies. You also need the
procedure declaration in a package declarative design unit (Those items visible to other design
units).
Note that this entity uses the type “operations” and must have access to the type declaration (you
will need to make minor modifications to the testbench ARCHITECTURE in regards to the
declaration for type operations ). Also remember the usage and function the of the USE clause
(re. Use Navabi as needed).
3) Compile and simulate your design.
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