ECE351 -  Homework #2  - Solved

 Write a SystemVerilog module that implements the schematic below using continuous assignment(s).  Note that there are no delays in the circuit.  

 
The signature for this module is:

 

module hw2_prob1 (  input logic  A, B, C, D,   output logic Y 

); 

 

 

B.  (10 pts) Write a testbench to verify the functionality of your model.  The testbench for this circuit should set up a $monitor() statement in one initial block and generate all of the possible input combinations with a #5 ns delay between changing the inputs.    

 

C.  (10 pts)  Simulate your model and your testbench using ModelSim or QuestaSim to demonstrate that your design is correct.  Submit a transcript of a successful simulation         

 (25
 

A.      (5 pts)  Write a SystemVerilog model of the following circuit.  Note that the buffer is a tri-state buffer.  Model the combinational logic using an always_comb block and the tri-state buffer using continuous assign statement(s):

 

  

 

The name of your module should be hw2_prob2.  You are the engineer for this project so we are leaving the signature of the module to you.  Note:  the inputs are x_in1..x_in5.  The tri-state output is y_out.

 

B.      (10 pts) Write a testbench to verify the functionality of your model.  The testbench for this circuit should set up a $monitor() statement in one initial block and generate all of the possible input combinations with a #5 ns delay between changing the inputs.  Be sure to check that y_out is ‘z whenever enable = 0.  Hint:  Declare y_out as a tri s that it is capable of be driven by more than one source. 

 

C.      (10 pts)  Simulate your model and your testbench using ModelSim or QuestaSim to demonstrate that your design is correct.  Submit a transcript of a successful simulation.        

 (50
For this homework problem we are going to create a SystemVerilog model for a simple digital system the includes an ALU (Arithmetic Logic Unit) with inputs taken from a 32 entry x 16 bit wide Register File and the results written back to the Register file.   A block diagram of the system is shown below:

 

 

 

   

A. (20 pts) Write a SystemVerilog module that implements an 8-bit ALU.  The ALU is a block of combinational logic that implements the following functionality (ex: ADD Opcode = 3’b000, EXNOR Opcode = 3’b111):

 

Opcode 
Operation 
Function 
3’b000
ADD
a + b + c_in
3’b001
SUBTRACT
a + ~b + c_in
3’b010
SUBTRACT_a
a + ~a + ~c_in
3’b011
OR_ab
{1’b0, a | b}
3’b100
AND_ab
{1’b0, a & b}
3’b101
NOT_ab
{1’b0, (~a) & b}
3’b110
EXOR
{1’b0, a ^ b}
3’b111
EXNOR
{1’b0, a ~^ b}
 

 Make use of SystemVerilog constructs as appropriate.  The signature for the module is:

 

import ALU_REGFILE_defs::*; 

 

module hw2_prob3_alu (  input logic [ALU_INPUT_WIDTH-1:0]  A_In, B_In, // A and B operands  input logic         Carry_In,       // Carry In 

 input aluop_t        Opcode,                         // operation to perform 

 output logic [ALU_OUTPUT_WIDTH-1:0]  ALU_Out          // ALU result(extended by 1 bit 

                                                       // to preserve Carry_Out from  

                                                       // Sum/Diff) 

);  

Note that the ALU Output is one bit wider than the inputs.  This is to preserve the Carry Out.  Note also the use of a typedef enum for the ALU opcode (operation to perform) in the ALU_REGFILE_defs package.    

B.  (15 pts) Create a model of the DUT called hw2_prob3_dut that instantiates instances of your ALU module and the register file module provided in the release.  Pad the extra bits from the ALU to the register file with 0’s. The signature for the module is: 

 

import ALU_REGFILE_defs::*; 

 

module hw2_prob3_dut ( 

 

 // register file interface 
 
 input  logic [REGFILE_ADDR_WIDTH-1:0] 
Read_Addr_1, // read port addresses  
             
Read_Addr_2, 
 input  logic [REGFILE_ADDR_WIDTH-1:0] 
Write_Addr, // write port address 
 input  logic         
Write_enable, // write enable (1 to 
             
              // write) 
 input  logic [REGFILE_WIDTH-1:0]   
Write_data, // data to write into the  
             
              // register file 
  

 // ALU interface.  Data to the ALU comes from the register file 

 input  logic         
Carry_In, 
// Carry In 
 input  aluop_t        
Opcode, 
// operation to perform 
 output logic [ALU_OUTPUT_WIDTH-1:0]  

  

 // system-wide signals 
ALU_Out, 
// ALU result 
 input  logic         

); 
Clock  
// system clock 
 

    

C.  (15 pts)  Simulate your source code with QuestaSim using the provided testbench to demonstrate that your design is correct.  Submit a transcript of a successful simulation. You will be graded on the correctness of your design.