CSC270 Exercises on Assembly Language

--D. Thiebaut 16:20, 27 March 2012 (EDT)

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Learning Assembly Through Exercises

Exercise 1

• Write a program that uses 3 byte variables, a, b, and c. The variable are initialized before the program starts with the values 2, 5, and 0, respectively.

• The program will add up the contents of the variable a to that of b and store the result into c. Only c will change.

Exercise 2

• Assemble the program of Exercise 1
• How many bytes does it contain?
• How fast will it go from beginning to end, assuming each 6811 cycle is 1 µsecond?

Exercise 3

• Same as Exercise 1, but for the Pentium.
• Assuming that the Pentium runs at a clock speed of 3 GHz, how many times could the program run on the Pentium while the same program run on the 1MHz 6811?

Exercise 4

• We want to compute Y = a + b - c + 3, where Y, a, b, and c are byte variables.
• Write the program that performs this operation.
• Assemble the program
• Count the total number of cycles it will take to run, and the total number of bytes it will use up in RAM.

Exercise 5

• Write a program that computes the first 5 terms of the fibonacci sequence, assuming that your program starts with 5 variables that all zero.
• Assemble it.
• How many cycles?
• How many bytes?

Pause

• Let's learn about direct addressing mode
• The excerpt below is taken from Introduction to 6811 Programming by Fred G. Martin.

Exercise 6

• Back to Exercise 4. Go through each instruction and identify the different addressing modes you used for each instruction.

Exercise 7

• Analyze the program below and make it shorter and/or faster. Your program should compute the same result as the original program.

	org	0
 	jmp	start

a	db	0
b	db	0
c	db	0

start:  ldaa	a
	inca
        staa	a
	ldaa	b
	inca
        inca
        staa    b
        ldaa	c
	inca
        inca
        inca
        staa	c
	jmp     start

Exercise 8

• Disassemble the program below. Its starting address is 011B:

011B  86
011C  01 F6 00
011F  1B
0120  1B 97 1B 7E
0124  01
0125  1B