EE319K_EXAM1_A_SOL_2010

EE319K_EXAM1_A_SOL_2010 - The return address of $403C is...

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EE319K Spring 2010 Exam 1A Solution Page 1 Jonathan W. Valvano February 24, 2010 2pm-2:50pm (5) Question 1. $A5 = 10100101 = -128+32+4+1 = -128+37 = -91 (5) Question 2. 0-9 is one decimal digital, and 0-3 is ¾ of a decimal digit. Part a) This system implements 4¾ decimal digits. Part b) 2 16 =65536 and 2 15 =32768. So, 40,000 alternatives would require at least 16 ADC bits. (5) Question 3. For the overflow (V) bit, convert both to signed and add -1+1=0. Since it fits, V=0. For the carry (C) bit, convert both to unsigned and add 255+1=256. Since it doesn’t fit, C=1. Since the result is zero, Z=1. (5) Question 4. This interface works because the LED current of 1 mA is less than the maximum output current of the 9S12, which is 1.6 mA. The current in the LED is controlled by the resistor. When the LED is on, there will be 1.9 V across the LED, so there will be 4.9-1.9= 3V across the resistor. To get an LED current of 1mA, set R = (4.9-1.9)/1mA = 3 k Ω . (10) Question 5.
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Unformatted text preview: The return address of $403C is pushed on the stack big endian, then the value of Register A is pushed $0A. SP points to the top SP -> $3FFD $0A $3FFE $40 $3FFF $3C (10) Question 6. The first three cycles fetch the entire instruction, the next two cycles fetch the 16-bi data at memory $0812. R/W Addr Data Changes to D,X,Y,S,PC,IR,EAR R $5000 $B3 IR=$B3, PC=$5001 R $5001 $08 PC=$5002 R $5002 $12 EAR=$0812, PC=$5003 R $0812 $00 R $0813 $00 (RegD is not changed) (10) Question 7. We use a 10k Ω pull-up resistor to implement a negative logic switch interface. PT1 9S12 +5 10 k Ω ;Solution to Question 8 ldd Sg ;needs 16-bit reg cpd #100 ;needs signed branch blt skip ;skip if Sg<100 bclr PTT,#$03 skip ReadPorts ;solution to Question 9 ldab PTT ; ? , ? , ? , ? ,PT3,PT2,PT1,PT0 lslb lslb lslb lslb ;PT3,PT2,PT1,PT0, 0 , 0 , 0 , 0 ldaa PTP ; ? , ? , ? , ? ,PP3,PP2,PP1,PP0 anda #$0F ; 0 , 0 , 0 , 0 ,PP3,PP2,PP1,PP0 aba ;PT3,PT2,PT1,PT0,PP3,PP2,PP1,PP0 rts...
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This note was uploaded on 11/03/2010 for the course EE 319K taught by Professor Bard during the Spring '08 term at University of Texas.

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