Questions and Answers of Digital Systems Design

Write synthesizable Verilog code that will generate the given waveform (W). Use a single always block. Assume that a clock with a 1 Î¼s period is available as an input. -43 μs -29 μs+
A BCD adder adds two BCD numbers (each of range 0 to 9) and produces the sum in BCD form. For example, if it adds 9 (1001) and 8 (1000) the result would be 17 (1 0111). Implement such a BCD adder
Write Verilog code for a shift register module that includes a 16-bit shift register, a controller, and a 4-bit down counter. The shifter can shift a variable number of bits depending on a count
(a) Figure 4-12 shows the block diagram for a 32-bit serial adder with accumulator. The control circuit uses a 5-bit counter, which outputs a signal K = 1 when it is in state 11111. When a start
A block diagram for a 16-bit 2€™s complement serial subtracter is given here. When St = 1, the registers are loaded and then subtraction occurs. The shift counter, C, produces a signal C15
(a) Construct an SM chart equivalent to the following state table. Test only one variable in each decision box. Try to minimize the number of decision boxes.(b) Write a Verilog description of the
This problem involves the design of a BCD-to-binary converter. Initially a 3-digit BCD number is placed in the A register. When an St signal is received, conversion to binary takes place and the
This problem involves the design of a circuit that finds the square root of an 8-bit unsigned binary number N using the method of subtracting out odd integers. To find the square root of N, we
This problem concerns the design of a multiplier for unsigned binary numbers that multiplies a 4-bit number by a 16-bit number to give a 20-bit product. To speed up the multiplication, a 4-by-4 array
(a) Estimate how many AND gates and adders will be required for a 16-bit × 16-bit array multiplier.(b) What is the longest delay in a 16 × 16 array multiplier, assuming an AND gate delay is tg, and
(a) Draw the organization of an 8 × 8 array multiplier and calculate how many full adders, half adders, and AND gates are required.(b) Highlight the critical path in your answer to (a). (If there
An n × n array multiplier, as in Figure 4-29, takes 3n - 4 adder delays + 1 gate delay to calculate a product. Design an array multiplier that is faster than this for n > 4. (Instead of passing
The block diagram for a multiplier for signed (2’s complement) binary numbers is shown in Figure 4-33. Give the contents of the A and B registers after each clock pulse when multiplicand = -1/8 and
In Section 4.10 we developed an algorithm for multiplying signed binary fractions, with negative fractions represented in 2’s complement.(a) Illustrate this algorithm by multiplying 1.0111 by
The objective of this problem is to use Verilog to describe and simulate a multiplier for signed binary numbers using Booth€™s algorithm. Negative numbers should be represented by their
Design a multiplier that will multiply two 16-bit signed binary integers to give a 32-bit product. Negative numbers should be represented in 2’s complement form. Use the following method: First
This problem involves the design of a parallel adder-subtracter for 8-bit numbers expressed in sign and magnitude notation. The inputs X and Y are in sign and magnitude, and the output Z must be in
Four pushbuttons (B0, B1, B2, and B3) are used as inputs to a logic circuit. Whenever a button is pushed, it is debounced, after which the circuit loads the button number in binary into a 2-bit
Design a 4 Ã— 4 keypad scanner for the following keypad layout.(a) Assuming only one key can be pressed at a time, find the equations for a number decoder given R3-0 and C3-0, whose
This problem concerns the design of a divider for unsigned binary numbers that will divide a 16-bit dividend by an 8-bit divisor to give an 8-bit quotient. Assume that the start signal (ST = 1) is 1
A block diagram and state graph for a divider for unsigned binary numbers is shown subsequently. This divider divides a 16-bit dividend by a 16-bit divisor to give a 16-bit quotient. The divisor can
A block diagram for a divider that divides an 8-bit unsigned number by a 4-bit unsigned number to give a 4-bit quotient is shown subsequently. The Xi inputs to the subtractors are shifted over one
An older model Thunderbird car has three left (LA, LB, LC) and three right (RA, RB, RC) tail lights, which flash in unique patterns to indicate left and right turns.Design a Moore sequential circuit
Design a sequential circuit to control the motor of a tape player. The logic circuit will have five inputs and three outputs. Four of the inputs are the control buttons on the tape player. The input
Complete the following Verilog code to implement a test bench for the sequential circuit SMQ1. Assume that the Verilog code for the SMQ1 sequential circuit module is already available. Use a clock
Write a test bench to test the counter of Problem 2.48. The test bench should generate a clock with a 100-ns period. The counter should be loaded on the first clock, then it should count for 5
Write a Verilog test bench that will test the Verilog code for the sequential circuit of Figure 2-58. Your test bench should generate all 10 possible input sequences (0000, 0001, 0010, . . .,1001)
Write Verilog code to test a Mealy sequential circuit with one input (X) and one output (Z). The code should include the Mealy circuit as a component. Assume the Mealy circuit changes state on the
A is an array of 20 4-bit registers. Write Verilog code that finds the largest register in the array,(a) Using a for loop.(b) Using a while loop.
Implement a 3-to-8 decoder using a LUT. Give the LUT truth table and write the Verilog code. The inputs should be A, B, and C, and the output should be an 8-bit unsigned vector.
(a) Write a Verilog module for a LUT with four inputs and three outputs. The 3-bit output should be a binary number equal to the number of 1s in the LUT input.(b) Write a Verilog module for a circuit
What device does the following Verilog code represent?reg Qtmp;always @(CLK,RST)beginif(RST == 1'b1)Qtmp = 1'b0;else if(CLK == 1'b1 && T == 1'b1)Qtmp = ~Qtmp;else beginendQ <= Qtmp;end
When the following Verilog code is simulated, A is changed to 1 at time 5ns. Make a table that shows all changes in A, B, and D and the times at which they occur through time = 40 ns. module
What is wrong with the following model of a 4-to-1 MUX? (It is not a syntax error.)reg [1:0]sel;always @(A,B,I0,I1,I2,I3)beginsel = 0;if(A == 1'b1)sel = sel + 1;elsebeginendif(B == 1'b1)sel = sel +
In the following code, state and nextstate are integers with a range of 0 to 2.always @(state,X)begincase(state)0:beginif(X == 1'b1)nextstate = 2'b01;end1:beginif(X == 1'b0)nextstate =
Write Verilog code to implement the following state table. Use two always blocks. State changes should occur on the falling edge of the clock. Implement the Z1and Z2outputs using concurrent
A Moore sequential machine with two inputs (X1and X2) and one output (Z) has the following state table:Write Verilog code that describes the machine at the behavioral level. Assume that state changes
(a) Write a behavioral Verilog description of the state machine that you designed in Problem 1.14. Assume that state changes occur on the falling edge of the clock pulse. Use a case statement
(a) Write a behavioral Verilog description of the state machine you designed in Problem 1.13. Assume that state changes occur on the falling edge of the clock pulse. Instead of using if-then-else
Examine the following Verilog code and answer the following questionsmodule Problem(X,CLK,Z1,Z2);input X,CLK;output Z1,Z2;reg [1:0]State,Nextstate;initialbeginState = 2'b00;Nextstate =
A synchronous 4-bit UP/DOWN binary counter has a synchronous clear signal CLR and a synchronous load signal LD. CLR has higher priority than LD. Both CLR and LD are active high. D is a 4-bit
Complete the following Verilog code to implement a counter that counts in the following sequence: Q = 1000, 0111, 0110, 0101, 0100, 0011, 1000, 0111, 0110, 0101, 0100, 0011, … (repeats). The
Consider the following 8-bit bidirectional synchronous shift register with parallel load capability. The notation used to represent the input/output pins is explained as follows:CLR Asynchronous
Write a Verilog model for a 74HC192 synchronous 4-bit up/down counter. Ignore all timing data. Your code should contain a statement of the form always @(DOWN,UP, CLR, LOADB).
A synchronous (4-bit) up/down decade counter with output Q works as follows: All state changes occur on the rising edge of the CLK input, except the synchronous clear (CLR). When CLR = 0, the counter
A description of a 74194 4-bit bidirectional shift register follows. The CLRb input is asynchronous and active low and overrides all the other control inputs. All other state changes occur
Write a Verilog module that describes a 16-bit serial-in, serial-out shift register with inputs SI (serial input), EN (enable), CK (clock, shifts on rising edge), and a serial output (SO).
A 4-bit magnitude comparator chip (e.g., 74LS85) compares two 4-bit numbers A and B and produces outputs to indicate whether A < B, A = B, or A > B. There are three output signals to indicate
Giveninteger A = 8'shA5;integer B = 8'shB6;integer C = 8'hA5;integer D = 8'hB6;reg signed [31:0] S;Evaluatei. S = A + B;ii. S = A + B + 0;iii. S = C + D;iv. S = C + D + 0;v. S = A + D;vi. S = A
Givenreg [3:0] A = 4'b1101;reg [2:0] B = 3'b111;reg signed [3:0] C = 4'b1101;reg signed [2:0] D = 3'b111;reg signed [7:0] S;Evaluatei. S = A + B;ii. S = A + B + 0;iii. S = C + D;iv. S = C
Write a Verilog description of an SR latch.(a) Use a conditional assignment statement (i.e., a behavioral description).(b) Use the characteristic equation in the Verilog description.(c) Use the logic
(a) Write at least two different Verilog modules that are equivalent to the following pseudo code:A = B1 when C = 1 else B2 when C = 2 else B3 when C = 3 else 0;(b) Draw a circuit to implement the
(a) Write a conditional signal assignment statement to represent the 4-to-1 MUX shown subsequently. Assume that there is an inherent delay in the MUX that causes the change in output to occur 10 ns
Draw the circuit represented by the following Verilog process:always @(clk,clr)beginif(clr == 1'b1)Q <= 1'b0;else if(clk == 1'b0 && CE == 1'b1)beginif(C == 1'b0)Q <= A & B;elseQ
Implement the following Verilog code using these components: D flip-flops with clock enable, a multiplexer, an adder, and any necessary gates. Assume that Ad and Ora will never be 1 at the same time
Consider the following Verilog code:module Q3(A,B,C,F,Clk,E);input A,B,C,F,Clk;output reg E;reg D,G;initialbeginE = 1'b0;D = 1'b0;G = 1'b0;endalways @(posedge Clk)beginD <= A & B & C;G
If A = 101, B = 011, and C = 010, what are the values of the following statements? Assume A, B, and C are of reg type. Assume as many bits as necessary for the result.(a) {A,B} | {B,C}(b) A >>
In the following Verilog Code, A, B, C, and D are registers that are 0 at time = 4 ns. If A changes to 1 at time 5 ns, make a table showing the values of A, B, C, and D as a function of time until
Given the following timing waveform for Y, draw D and E.wire #3 D; // net delay on wire Dassign #5 D = Y; // statement 1 - inertial delaywire #5 E; // net delay on wire Eassign #3 E = Y; // statement
Given the following timing waveform for Y, draw D and E.wire #4 D; // net delay on wire Dassign #6 D = Y; // statement 1 2 inertial delaywire #6 E; // net delay on wire Eassign #4 E = Y; // statement
Assuming B is driven by the simulator command:force B 0 0, 1 4, 0 10, 1 15, 0 20, 1 30, 0 40Draw a timing diagram illustrating A, B, and C if the following statement is executed:(a) always
Assuming B is driven by the simulator command:force B 0 0, 1 4, 0 10, 1 15, 0 20, 1 30, 0 40Draw a timing diagram illustrating A, B, and C if the following concurrent statements are executed:always
Assuming B is driven by the simulator command:force B 0 0, 1 10, 0 15, 1 20, 0 30, 1 35Draw a timing diagram illustrating A, B, and C if the following concurrent statements are executed:always
For the following Verilog code, assume that D changes to 1 at time 5 ns. Give the values of A, B, C, D, E, and F each time a change occurs. That is, give the values at time 5 ns, 5 + D, 5 + 2D, and
What is wrong with the following code for a half adder that must add if add signal equals 1?always @(x)beginif (add == 1)beginsum = x ^ y;carry = x & y;endelsebeginsum = 0;carry = 0;endend
(a) Assume D1 = 0, D2 = 5, and D1 changes to 1 at time = 10ns. What are the values of D1 and D2 after the following code has been executed once? Do the values of D1 and D2 swap?always @
Draw the hardware obtained if the following two modules are synthesized and describe the differences.module reg3 (Q1,Q2,Q3,Q4,A,CLK);input A;input CLK;output Q1,Q2,Q3,Q4;reg Q1,Q2,Q3,Q4;//
Draw the hardware obtained if the following code is synthesized:module reg3 (Q1,Q2,Q3,Q4, A,CLK);input A;input CLK;output Q1,Q2,Q3,Q4;reg Q1,Q2,Q3,Q4;always @(posedge CLK)beginQ1 = A;Q2 = Q1;Q3 =
Givenreg [7:0] C;reg signed [7:0] D;reg [7:0] A = 8'shD5;Evaluatei. C = A >> 4ii. C = A >>> 4iii. C = A << 4iv. C = A <<< 4v. D = A >> 4vi. D = A >>>
Givenreg [7:0] C;reg signed [7:0] D;reg [7:0] A = 8'hD5;Evaluatei. C = A >> 4ii. C = A >>> 4iii. C = A << 4iv. C = A <<< 4v. D = A >> 4vi. D = A >>> 4vii.
EvaluateA >> 4A >>> 4A << 4A <<< 4given(a) reg signed [7:0] A = 8'hC7;(b) reg [7:0] A = 8'hA5;(c) reg signed [7:0] A = 8'hC7;(d) integer signed A = 8'hC7;(e) integer A =
Givenreg [7:0] C;reg signed [7:0] D;reg signed [7:0] A = 8'hD5;evaluatei. C = A >> 4ii. C = A >>> 4iii. C = A << 4iv. C = A <<< 4v. D = A >> 4vi. D = A
Givenwire a = 1'b0;wire [1:0] b = 2'b10;wire [2:0] c = 3'b101;Evaluatei. { 4{a} }ii. { 4{a}, 2{b} }iii. { 4{a}, c}
Givenwire a = 1'b1;wire [1:0] b = 2'b10;wire [2:0] c = 3'b101;Evaluatei. {b, c}ii. {a, b, c, 2'b01}iii. {a, b[0], c[1]}
Draw the hardware obtained if the following code is synthesized:module reg3 (Q1,Q2,Q3,Q4, A,CLK);input A;input CLK;output Q1,Q2,Q3,Q4;reg Q1,Q2,Q3,Q4;always @(posedge CLK)beginQ4 = Q3;Q3 = Q2;Q2 =
In the following Verilog process A, B, C, and D are all registers 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
In the following Verilog process A, B, C, and D are all registers that have a value of 0 at time = 10ns. If E changes from 0 to 1 at time = 20ns, specify the time(s) at which each signal will change
An inhibited toggle flip-flop has inputs I0, I1, T, and Reset and outputs Q and QN. Reset is active high and overrides the action of the other inputs. The flip-flop works as follows: If I0 = 1, the
A DD flip-flop is similar to a D flip-flop, except that the flip-flop can change state (Q+ = D) on both the rising edge and the falling edge of the clock input. The flip-flop has a direct reset
An M-N flip-flop responds to the falling clock edge as follows:If M = N = 0, the flip-flop changes state.If M = 0 and N = 1, the flip-flop output is set to 1.If M = 1 and N = 0, the flip-flop output
Write a Verilog description of an S-R latch using an always block.
(a) What device does the following Verilog code represent?always @(CLK, Clr, Set)beginif(Clr == 1'b1)Q <= 1'b0;else if(Set == 1'b1)Q <= 1'b1;else if(CLK == 1'b0)Q <= D;else beginendend(b)
In the following Verilog code, A, B, C, and D are 0 at time 10 ns. If D changes to 1 at 20 ns, specify the times at which A, B, and C will change and the values they will take.(a) always
Write Verilog code for the following circuit. Assume that the gate delays arenegligible.(a) Using concurrent statements.(b) Using an always block with sequential statements. No latches should be
(a) Write Verilog code for a full subtracter using logic equations.(b) Write Verilog code for a 4-bit subtracter using the module defined in (a) as a component.
Write a Verilog description of the following combinational circuit using concurrent statements. Each gate has a 5-ns delay, excluding the inverter, which has a 2-ns delay. C - ABCDAR
Given the concurrent Verilog statements:assign #3 B = A && C;assign #2 C = !B;(a) Draw the circuit the statements represent.(b) Draw a timing diagram if initially A = B = 0 and C = 1, and A
(a) Which of the following are legal Verilogidentifiers? 123A, A_123, _A123, $A123_, c1__c2, and, and1(b) Which of the following Verilogidentifiers are equivalent? aBC, ABC, Abc, abc
(a) What do the acronyms HDL and FPGA stand for?(b) How does a hardware description language like Verilog differ from an ordinary programming language?(c) What are the advantages of using a hardware
A simple binary counter has only a clock input (Ck1). The counter increments on the rising edge of Ck1. (a) Show the proper connections for a signal En and the system clock (CLK), so that when
Referring to Figure 1-56, specify the values of Eni, Ena, Enb, Enc, Lda, Ldb, and Ldc so that the data stored in Reg. C will be copied into Reg. A and Reg. B when the circuit is clocked. Eni Input N
(a) Do the following two circuits have essentially the same timing?(b) Draw the timing for Qaand Qbgiven the timing diagram.(c) If your answer to (a) is no, show what change(s) should be made in the
A Mealy sequential machine has the following state table:Complete the following timing diagram. Clearly mark on the diagram the times at which you should read the values of Z. All state changes occur
Consider the following circuit where the combinational circuit is represented by COMB and clock skew is represented by tskew. Given the following parameters: FF setup time = 10 nsFF hold
Consider the following circuit where the combinational circuit is represented by COMB and clock skew is represented by tskew.Given the following parameters:FF setup time = 20 ns FF hold time =
In the following circuit, the XOR gate has a delay in the range of 2 to 16 ns. The D flip-flop has a propagation delay from clock to Q in the range 12 to 24 ns. The setuptime is 8 ns, and the hold
In the following circuit, the XOR gate has a delay in the range of 2 to 16 ns. The D flip-flop has a propagation delay from clock to Q in the range 12 to 24 ns. The setup time is 8 ns, and the hold
A D flip-flop has a propagation delay from clock to Q of 15 ns. The setup time of the flip-flop is 10 ns, and the hold time is 2 ns. A clock with a period of 50 ns (low until 25 ns, high from 25 to
A sequential circuit consists of a PLA and a D flip-flop, as shown in the following diagram.(a) Complete the timing diagram assuming that the propagation delay for the PLA is in the range 5 to 10 ns
A D flip-flop has a propagation delay from clock to Q of 7 ns. The setup time of the flip-flop is 10 ns, and the hold time is 5 ns. A clock with a period of 50 ns (low until 25 ns, high from 25 to 50

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