exam2006 - CITY UNIVERSITY OF HONG KONG Course code &...

CITY UNIVERSITY OF HONG KONG
Course code & title: EE3120 Microprocessor and Assembly Language Programming
Session : Semester A, 2006-2007
Time allowed : Two hours
This paper has 12 pages (including this cover page).
Instructions to candidates:
1. This paper consists of FOUR questions.
2. Answer any THREE questions.
3. Use a separate sheet for each question.
Materials, aids & instruments permitted to be used during examination: Approved
calculator.
NOT TO BE TAKEN AWAY
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Question 1 (34 marks)
(a)
(i) State the meaning of Register-Specific Addressing and give an example of this mode
of addressing that involves moving data.
[5 marks]
(ii) Explain the usage of the instructions MOVC and MOVX and give an example for each
of these instructions.
[5 marks]
(b)
(i) Define the meanings of a stack and stack pointer? Why the stack pointer is needed?
[5 marks]
(ii) Suppose an 8051 microcontroller is used in this question . Show the contents of the
stack and stack pointer after execution of the instruction for each line of the
following program. (The PUSH and POP instructions only occupy 1 byte of the
memory .)
ORG 0
MOV SP,#70H
MOV R5,#22H
MOV R2,#3FH
MOV R7,#3EH
PUSH 5
PUSH 2
PUSH 7
CLR A
MOV R2,A
MOV R7,A
POP 7
POP 2
POP 5
[6 marks]
(c)
(i) Write a program to check if bits 0 and 3 of register B are 1. If they are not, make them
so and save them in R5. Note that the RAM location of B is F0H and is a n 8-bit
register.
[5 marks]
(ii) Assume that RAM bit location 1 0 H holds the status of phone call. If it is high, that
means there has been a new call since it was checked the last time. Write a program to
display “ Phone Call ” on a LCD if bit RAM 1 0 H is high. If it is low, the LCD should
display “ No Phone Calls ”. Suppose the subroutine for displaying the messages on the
LCD is called “ DISPLAY ” and has been written. You can simply call this subroutine
directly and do not need to re-write it again.
[ 8 marks]
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