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ECE 367 - Microprocessor-Based Design Midterm Examination (7 pages, 26 problems: 50 minutes, closed book and notes.) No electronic devices other than a calculator are permitted.
IMPORTANT: Please be aware that academic dishonesty will result in grade E for the course, and possibly dismissal from the University. Looking at another exam paper, showing someone your exam paper, violating the closed book/notes rule, or otherwise communicating exam problem information to/from another student during the exam is considered to be academically dishonest. Should you have any questions about this policy or about any of the exam questions, please step up to the front and ask the instructor for clarification.
1. What value is represented by the byte $A3 when the code being used is
a) unsigned binary:
(
)10
b) signed binary:
(
)10
2. What value is represented by the byte $3A when the code being used is ( )10
a) unsigned binary:
b) signed binary:
(
)10
2003 University of Illinois at Chicago
ECE 367 V. Goncharoff
3. What are the values of C and V flags after these 68HC11 assembly language instruction are executed?
LDAA #$FF INCA
C=
, V=
4. Translate the following 68HC11 assembly language instructions into machine code (the first one is done for you):
LDAB 0,Y BRA * ADDD #10 $18 __$E6__ $00_ ________________ ________________
5. (Circle only one letter) Which of these 68HC11 instructions takes longest to execute? a) b) c) d)
INC 0,Y CMPB #$0A RTS RTI
6. (Circle only one letter) Which of these 68HC11 instructions has the longest machine code? a) b) c) d)
INC 0,Y CMPB #$0A RTS RTI
7. (Circle only one letter) Which of these 68HC11 instructions does not change the stack pointer register contents? a) b) c) d)
JSR Delay JMP Delay RTS RTI
2003 University of Illinois at Chicago
ECE 367 V. Goncharoff
8. Assume that IX has already been initialized to $1000, and symbol PORTB has been equated with $04. Write a single 68HC11 instruction that clears bits {PB0, PB7} without affecting the state of any other bits in Port B:
9. Assume that IX has already been initialized to $1000, and symbol TFLG2 has been equated with $25. Write a single 68HC11 instruction that loops to itself until the TCNT timer overflow flag becomes set:
10. What are the contents of register IY after instruction "LDY Here" executes in the code below?
ORG Here: LDY Here $FF00
$ __ __ __ __
11. How many clock cycles of delay is introduced by calling subroutine "Delay" below? Round your answer to the nearest billion.
Delay: PSHY LDY PSHY LDY DEY BNE PULY DEY BNE PULY RTS #65535 #65535 A2 (5) (4) (5) (4) (4) (3) (6) (4) (3) (6) (5)
A1: A2:
A1
Answer: billion clock cycles
2003 University of Illinois at Chicago ECE 367 V. Goncharoff
12. What is the duty cycle of the waveform produced at PORTB by the endless loop EQU below?
PORTB LDX LDAA STAA LDAA STAA NOP NOP NOP BRA $04 #$1000 #$00 PORTB,X #$FF PORTB,X (2) (4) (2) (4) (2) (2) (2) (3)
Loop:
%
Loop
13. Given that the frequency of E clock is 2 MHz, what is the frequency of the PORTB waveform produced by the endless loop below? (The number of clock cycles per instruction are shown in parentheses.)
PORTB EQU $04 LDX #$1000 CLRA EORA STAA BRN EORA STAA BRN EORA STAA BRA #$FF PORTB,X Loop #$FF PORTB,X Loop #$FF PORTB,X Loop (2) (4) (3) (2) (4) (3) (2) (4) (3)
Loop:
Hz
14. Write code to clear flag OC2F:
2003 University of Illinois at Chicago
ECE 367 V. Goncharoff
15. When writing interrupt-driven code to produce a PWM waveform at PA4 of the M68HC11E, what two TOC registers would you use for this purpose?
TOC__ ,
TOC__
16. What prescaling factor and TCNT value would you use when writing interrupt-driven code to execute exactly every 0.001 sec? (E = 2MHz) More than one correct answer may exist; write only one answer below: Prescaling factor N = ___ , TCNT = ____________
17. With circuit below, what bit pattern should be sent to Port B to have the seven-segment common-cathode LED to display digit "4"?
common cathode PB0 MC68HC11 microcontroller a b c d e f g f e d a g b c
PB1 PB2 PB3 PB4 PB5 PB6 PB7
Port B = $ __ __
18. In Problem 17 control signal PB0 is: a) active high b) active low
(circle a or b)
19. In Problem 17 control signals {PB1-PB7} are: a) active high
2003 University of Illinois at Chicago
(circle a or b)
b) active low
ECE 367 V. Goncharoff
20. For the matrix keypad interface circuit below, write instructions that loop until key "8" is pressed. You may assume that Port C has been properly configured for both input and outp...