Questions

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Problem 1—If you have 24 people in a room, what are the chances that any two of them have the same birthday? ANSWER Problem 2—Each Ethernet device has a 48-bit address (the MAC) that is supposed to be unique. If the MACs are chosen randomly, how many devices can be manufactured before there's a better-than-even chance that two of them have the same MAC? ANSWER Problem 3—Suppose a small manufacturer, who needs to make about 100 Ethernet devices, decides to generate random MACs instead of going to the expense and trouble of getting an OUI (organizationally unique identifier) from the IEEE. Assuming that there are 100,000,000 devices out there that are known to have unique MACs, what are the chances that they'll duplicate an existing MAC? What if 100 manufacturers do this (10,000 devices)? ANSWER Problem 4—Do Ethernet MACs need to be locally unique (within a given LAN) or globally unique? Why? Answer 4 ANSWER Problem 5—The value of R in the oscillator circuit shown below is chosen so that it just oscillates at an angular frequency of w. Calculate the value of R and w. ANSWER Problem 6—A zener diode in the circuit shown in the figure has a knee current of 5mA, and a maximum allowed power dissipation of 300mW. What are the minimum and maximum currents that can be drawn safely by the load, keeping the output voltage Vo constant at 6V? ANSWER Problem 7—In the cascade amplifier shown below, determine the values of R1, R2 and R such that the quiescent current through the transistors is 1mA and the collector voltages V_C1 = 3 V and V_C2 = 6 V. Take V_BE = 0.7 V and assume the transistor current gain factor h_FE to be high and base currents to be negligible. For extra credit, redo the calculation with the assumption that h_FE is 100. ANSWER Problem 8—An 8085 microprocessor uses a 2MHz crystal. Find the time taken by it to execute the following delay subroutine, including the CALL instruction in the calling program. DELAY: PUSH PSW MVI A,64H DELAYLOOP: NOP DCR A JNZ LOOP POP PSW RET The CALL and RET instructions each take 18 cycles of the system clock, PUSH and POP take 12 cycles each, and conditional jump takes 10 cycles if the jump is taken and 7 cycles if is not. NOP takes 1 cycle. All other instructions used above take (3 � N + 1) clock cycles, where N is the number of accesses to memory, not including the opcode fetch. ANSWER 03-02