Coursehero >> California >> UCSD >> ECE 20

Course Hero has millions of student submitted documents similar to the one below including study guides, homework solutions, papers, exam answer keys and textbook solutions.

Midterm ECE20B 2, 100 Point Exam Closed Book, Closed Notes, Calculators Allowed May 24th, 2001 Name Guidelines: Place your name at the upper right-hand corner of every page you turn in. Please use your own paper or examination book. You may put the answer to problems 1, 2, 7, and 9 on the provided gures, but write answers to all other questions on a di erent sheet of paper. Number your problems clearly. You must turn in the exam sheets as well as your answers. Please do not write in the following box. This will be used by the graders to record their scores. Prob Score Prob Score Prob Score 1 5 9 2 6 10 3 7 4 8 1. (10 points) Assume that you are given a priority encoder with inputs A, B, C, and D and output F and error ag ER. Assume that the variable A has the highest priority, followed by B, C, and D (in that order). Fill in the truth table given below. Only 5 rows should be required if you use don t care notation. Note: there is more than one solution to this problem. A 1 0 0 0 0 B X 1 0 0 0 C X X 1 0 0 D X X X 1 0 S1 0 0 1 1 X S2 0 1 0 1 X ER 0 0 0 0 1 2. (10 points) Draw the logic circuit for F (A, B, C) = A B C using a 3-to-8 decoder (see Figure 1). 3. (10 points) Assume that you are given a pair of unsigned two-bit numbers, namely A (represented by A1 and A0 ), and B (represented by B1 and B0 ). Draw the logic circuit for A B (the multiplication of A by B) using half-adders and full-adders (see Figure 2), and whatever additional gates you deem necessary. 4. (10 points) Assume that you are given the decimal numbers A = 23 and B = 99. (a) Express A and B as signed 8-bit binary numbers using 2s complement notation. (b) Show how A + B is calculated using 2s complements. Your nal answer should be left in 2s complement form. 5. (10 points) What is a sequential circuit and how does it di er from a combinational circuit? 1 1. Logic gates: a. (5 points) For the logic circuit from the enter key detector of the robot (Figure 4) give the outputs at E and F in terms of A, B, C, D inputs. Do the truth table relating A, B, C, D, E and F. A F B E C D Figure 4 E=BCD F=ABCD A 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 B 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 C 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 E 1 0 1 0 1 0 1 1 1 0 1 0 1 0 1 1 F 1 1 1 1 1 1 1 1 0 1 0 1 0 1 0 0 2. For the rising edge triggered D Flip Flop (as shown Figure in 5): a. (3 points) Describe the function of each port. The D is the data input terminal. The C is the clock. The Q and Q are the outputs. The value of the Q output becomes whatever the value of the D input was at the time of the clock changing from logic 0 to logic 1. The Q is always the opposite of Q. The S and R are the set and reset. When either of them logic 1 they override the D input and regardless of the clock make Q a 1 or 0, respectively. b. (5 points) Assume that S and R ports are grounded and that the inputs to C and D ports are shown in Figure 6. Draw the waveforms at ports Q and Q. You may assume that initially Q=0 and Q=1. S D Q C D C Q Q R Q Figure 5 time Figure 6 3. Memory system: ATTENTION: There was an error in Figure 7. The output pins were incorrectly marked from Q0 to Q11. The correct sequence is from Q1 to Q12. a. (3 points) How many of the 12 output pins of the counter chip 4040 (Figure 7) were used in the lab and what happened to the rest? What is the order of the bits on the counter chip? 8 output pins were used as an address and Q9 was an address overflow indicator. The remaining three pins were not connected. Q1 is the LSB and Q8 is the MSB. b. (3 points) What are the functions of CLOCK, RESET and Q9 lines? The CLOCK input will increment the counter. The RESET will reset the counter to zero when high. The Q9 output is connected to the memory chip select (CS) input and to LED driver. When this pin goes high it disables the memory and turn on the LED indicating an overflow condition. c. (3 points) How many address pins are on the memory chip 5101 (Figure 8)? How many address locations? There are 8 address pins, 256 address locations. d. (3 points) What are the functions of pins 20 (R/W), 17/19 (CS/CS) and 18 (OD)? When the enter key is pressed the R/W pin pulses low and the data that present on the Data-In pins is stored at the location addressed. When the CS/CS is low/high it disables the operation of the memory IC. This prevents the address overflow. When the OD is low the output data will appear at the Data-Out pins. 5V 1 2 3 4 5 6 7 8 Q12 Q6 Q5 Q7 Q4 Q3 Q11 Q10 Q8 Q9 RESET 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 9 10 A in A out B in Fi R/W CS OD CS D out D in C out C in B out 5V 22 21 20 19 18 17 16 15 14 13 12 Figure 4. 4040 counter Q2 CLOCK Q1 Figure 7. 4040 counter 11 Figure 8. 5101 SRAM

Find millions of documents here - Study Guides, Homework Solutions, Papers, Exam Answer Keys and more. Course Hero has millions of course related materials that will enable you to learn better, faster and get an A in all your courses.
Below is a small sample set of documents: