ECE 448: Spring 12 Lab Midterm Exam Review

Part 1: Detailed discussion of a selected midterm from Spring Part 2: Review & discussion of common mistakes made by students in Lab 1-3 Part 3: Lab demos and grading Agenda for today

Selected midterm from Spring 2011

Common mistakes made by students in Lab 1-3

Assert condition: o The message is written when the condition is FALSE. assert initial_value <= max_value report "initial value too large" severity error; Mistakes in Lab 1

Use of Test vector table and Output Comparison Test Vector Table: CONSTANT test_vector_table: test_vectors := ( (operation => AND_OP, a=>'0', b=>'0', y=>'0'), (operation => AND_OP, a=>'0', b=>'1', y=>'0'), (operation => AND_OP, a=>'1', b=>'0', y=>'0'), (operation => AND_OP, a=>'1', b=>'1', y=>'1'), (operation => OR_OP, a=>'0', b=>'0', y=>'0'), (operation => OR_OP, a=>'0', b=>'1', y=>'1'), (operation => OR_OP, a=>'1', b=>'0', y=>'1'), (operation => OR_OP, a=>'1', b=>'1', y=>'1'), (operation => XOR_OP, a=>'0', b=>'0', y=>'0'), (operation => XOR_OP, a=>'0', b=>'1', y=>'1'), (operation => XOR_OP, a=>'1', b=>'0', y=>'1'), (operation => XOR_OP, a=>'1', b=>'1', y=>'0'), (operation => XNOR_OP, a=>'0', b=>'0', y=>'1'), (operation => XNOR_OP, a=>'0', b=>'1', y=>'0'), (operation => XNOR_OP, a=>'1', b=>'0', y=>'0'), (operation => XNOR_OP, a=>'1', b=>'1', y=>'1') ); Providing Input: test_operation <= test_vector_table(i).operation; test_a <= test_vector_table(i).a; test_b <= test_vector_table(i).b; Comparing Output: IF test_y /= test_vector_table(i).y THEN error_cnt := error_cnt + 1;

Choosing proper libraries: o USE ieee.numeric_std.all; o USE ieee.std_logic_unsigned.all ; o USE ieee.std_logic_signed.all ; Opcodes: o Rotation right with Carry by 2 o Arithmetic Shift Right by 3 with Rounding o Variable Rotation Right o Variable Logic Shift Left o Variable Arithmetic Shift Right with Rounding o Variable Logic Shift Right Mistakes in Lab 2

Difference between Dataflow, Structural and Behavioral coding styles o Dataflow: Concurrent statements o Structural: Components and Interconnects o Behavioral: Processes Difference between Combinational and Sequential logic o Combination: Not dependent on Clock o Sequential: Dependent on Clock (Registers, Shift registers. Counters, State machines)

o Use of Generics o Shift Register Mistakes in Lab 3

Variable left shift

Use of Generics and For Generate: Variable 16-bit rotator TYPE array1 IS ARRAY (0 to 4) OF STD_LOGIC_VECTOR(15 DOWNTO 0); TYPE array2 IS ARRAY (0 to 3) OF STD_LOGIC_VECTORS(15 DOWNTO 0); SIGNAL Al : array1; SIGNAL Ar : array2; BEGIN Al(0) <= A; G: FOR i IN 0 TO 3 GENERATE ROT_I: fixed_rotator_left_16 GENERIC MAP (L => 2** i) PORT MAP ( a => Al(i), y => Ar(i)); MUX_I: mux2to1_16 PORT MAP ( w0 => Al(i), w1 => Ar(i), s => B(i), f => Al(i+1)); END GENERATE; C <= Al(4); END variable_rotator_16;

Shift Register With Parallel Load D(3) DQ Clock Enable Sin D(2) DQ D(1) DQ D(0) DQ Q(0)Q(1)Q(2)Q(3) Load

LIBRARY ieee ; USE ieee.std_logic_1164.all ; ENTITY shiftn IS GENERIC ( N : INTEGER := 8 ) ; PORT (D : IN STD_LOGIC_VECTOR(N-1 DOWNTO 0) ; Enable: IN STD_LOGIC ; Load: IN STD_LOGIC ; Sin : IN STD_LOGIC ; Clock : IN STD_LOGIC ; Q : OUT STD_LOGIC_VECTOR(N-1 DOWNTO 0) ) ; END shiftn ; N-bit shift register with parallel load (1) Q Enable Clock shiftn N D Load Sin N

ARCHITECTURE behavioral OF shiftn IS SIGNAL Qt: STD_LOGIC_VECTOR(N-1 DOWNTO 0); BEGIN PROCESS (Clock) BEGIN IF rising_edge(Clock) THEN IF Enable = ‘1’ THEN IF Load = '1' THEN Qt <= D ; ELSE Qt <= Sin & Qt(N-1 downto 1); END IF; END PROCESS ; Q <= Qt; END behavior al; N-bit shift register with parallel load (2) Q Enable Clock shiftn N D Load Sin N

Lab 4 Demos