Summer 2007 ECE 3055
Assignment 2
Due Date: 11:59 pm, Monday June 4th, 2007.
Part I: SPIM Programming
Purpose:
To understand and apply shift, masking, and logical operations and the MIPS 32
procedure calling conventions
Goal
You will write a SPIM program that performs arithmetic on packed byte values. Recall
that four byte values can be packed into one word. Using the .byte data directive store an
array of 64 byte values (pick your own values) in the data segment. Use the .word
directive if you like. If we are initializing the byte array to random values you can see
that it does not really matter whether we use the .byte or .word directives!
Compute a new byte array which we will designate as the output array. This array is also
packed into words. The values in this array denote the location of “edges” in the original
array. An element at index i in the original array is an edge if the difference between
element i and element i+1 is greater than a threshold value. For example consider the
sequence of element values as follows.
2 4 3 8 5 2 9 1 1.....
The edge values for a threshold of 4 will be
0 0 1 0 0 1 1 0.....
Your program should query the user for a threshold value and only accept values between
0-63. If the value falls outside this range, the user should be queried again.
Requirements
Your solution should have the following procedures and control structure.
1. Given an index and the start of the array, a procedure with label getval that returns
the thresholded value at that index.
2. Given an index, the start of the array, and a 32-bit register, a procedure with label
putval that writes the least significant byte to that location.
3. A procedure, thresh, for computing the thresholded (0/1) value given three
element values.
4. Your program iteratively calls getval which in turn calls thresh.
5. Write a procedure to print an array to the console. On completion print out both
the values of the input array and output array. This is the last operation in the
program.
