04s_cpe422_midterm_solution - The University of Alabama in...

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The University of Alabama in Huntsville ECE Department CPE/EE 422/522 01 Midterm Exam Solution 1. (4 points) In general, what are static hazards in a combinational network. Static hazards occur when an output has the wrong value temporarily due to propagation delay difference down multiple paths or simultaneous changes on multiple inputs. 2. (5 points) Obtain a minimum sum of products expression for the following function: f(A, B, C, D) = Σ m(0, 1, 2, 5, 8, 9, 10, 13) A D B 1 1 1 1 1 1 1 1 C fC DB D =+ 3. (7 points) Write a short VHDL description of a negative edge-triggered D flip-flop using a VHDL process. entity DFF is port (D, CLK : in bit; Q, QBAR : out bit); end DFF; architecture DFF of DFF is begin process (CLK) begin if (CLK’event and CLK = ‘0’) then Q <= D; QBAR <= not D; end if; end process; end DFF; 4. (15 points) In the following VHDL process A, B, C, and D are all integers that have a value of 0 at time – 10 ns. If E changes from ‘0’ to ‘1’ at time 20 ns, specify the time(s) at which each signal will change and the value to which it will change. List these changes in chronological order. List any delta delays as a separate entry. P1: process begin wait on E; A <= 1 after 5 ns; B <= A + 1; wait for 0 ns; C <= B after 10ns; D <= A after 3 ns; A <= A + 5 after 15 ns;
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B <= B + 7; end process P1; Time A B C D
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This note was uploaded on 07/22/2011 for the course CPE 422 taught by Professor Staff during the Fall '09 term at University of Alabama - Huntsville.

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04s_cpe422_midterm_solution - The University of Alabama in...

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