1. Convert the following MIPS assembly fragment into C code. Assume integer a is
associated with register $s0, integer b is associated with $s1, and integer result is associated
with register $s2. slt $t0, $s1, $s0 beq $t0, $zero, L1 sub $s0, $s0, $s1 j L3
L1: slt $t0 $s0, $s1 beq sub j
$t0, $zero, L2
$s1, $s1, $s0
L3
L2: add $s2, $zero, $s0
L3:

2.
a. What is the logic equation represented by the hardware logic above?
b. Fill in the truth table according to the logic equation you provided in part a.
A B C D
0
0
0
0
0
1
0
1
0
0
1
1
1
1
0
0
1
1
0
1
0
1 1 1

c. Express the logic equation in the canonical sum-of-products form and redraw the
hardware to directly implement the sum-of-products form of the equation.
d. What if we added another output E, describe by the following truth table. How can we
modify our hardware to perform E as well?
A B C E
0
0
0
0
0
1
0
1
0
1
0
1
0
1
1
1
1
0
0
1
1
0
1
0
0
0
0
0
1 1 1 1

3. a. Fill in the single-cycle datapath below so that it implements the store word
instruction. An example store word instruction is sw $s0, 4($s1). Furthermore, indicate the
bit size of each of the input and output lines being used in the datapath using the notation
we’ve seen in class. For the following control lines, indicate whether each one needs to be
set or unset for the store word instruction. Note that you may not need all of the state
elements depicted.
Control Line
RegWrite
MemWrite
MemRead
Set or Unset?

b. Assume we want to add a new instruction to our instruction set. This instruction is
called load add register, or lar. An example load add register instruction is lar $s0, $s1, $s2.
This instruction retrieves the contents of a memory address stored in $s1 and adds the
contents to the value stored in $s2. The results are stored in register $s0. In other words, this
instruction is equivalent to the following sequence of instructions: lw $t0, 0($s1) add $s0, $s2, $t0
Create a datapath for this instruction. Label each of the input and output lines with their
width in bits. In the table below, indicate which control lines need to be set for this
instruction to be executed. Note that you may not need all of the state elements depicted.
Control Line
RegWrite
MemWrite
MemRead
Set or Unset?