CSC270 Homework 7 2012

--D. Thiebaut 13:43, 28 March 2012 (EDT)

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This homework assignment is due on 4/4/12, at 1:00 p.m. You may work on this lab in teams of at most 2 people.

Problem #1

Disassemble the code you used in the lab to display your message. This requires looking up the op-codes and figuring out what instructions they correspond to, and write the whole program using mnemonics.

The reverse table found here will help you do the reverse engineering.

Problem #2

Question 1

Using the same idea as the "Hacking" problem in the last lab (putting your name into the display of the kit), pick a message that you want to display, and hack the code you used in the lab to make it display your code.

Take a picture (or several pictures) of the display showing your message and include it/them with your answer

Question 2 (optional extra credit)

Write the code of your hacked program in assembly using the knowledge you acquired in Problem 1.

Problem #3

Question 1

• Write a program in 6800 Assembly Language that computes the quantity

        Y =  3 * ( a + b ) - ( c - 2 )

where Y, a, b, and c are byte variables.

• Assemble your code by hand.
• Write the listing of your code in a format similar to the example below:

       ORG   0000    ; specifies starting address 0000
 
       LDAA  a       ; get Mem[0000] in ACCA (direct addressing) 
       LDAB  b       ; get Mem[0001] in ACCB
       ABA           ; ACCA <- ACCA + ACCB
       STAA  c       ; Mem[0002] <- ACCA

       ORG  0010    ; specifies starting address 0

a      DB    2       ; 2 is stored at 0010
b      DB    3       ; 3 is stored at 0011
c      DB    ?       ;

• Make sure you include the opcodes on the left of the program, including the address for each instruction.

Question 2

• How many bytes of code plus data does your program take?

Question 3

• How many cycles does your program take to execute from first to last instruction.