Homework Set 4
DUE: Monday, Nov. 4
, 2002, Start of class
Collaboration Policy:
Unless otherwise noted, you may collaborate with other CSE370 students on the homework assignments. Do not look at homework or exam solutions from previous years. You must spend at least 15 minutes working on a problem before seeking assistance. Collaboration means that you may discuss the problems and make notes during the discussion, but you may not look at other student’s work when writing up your homework. Your homework represents your own work—the homework must show that you understand the material and have worked as an individual on every problem. You may not divide up the task of doing the problem sets in the interpretation of collaboration. You may discuss lecture material with anyone.
Late Homework Policy:
The weekly assignments are due at the beginning of class. Assignments handed in during or immediately after class will incur a 10% penalty. We will penalize your assignment 10% per day for each additional day late.
Please show all of your work.Your solutions must be legible…we will not spend time trying to decipher poorly written assignments.
Corrections made after the assignment was handed out are highlighted in red.
1. (25 points) Use the accompanying worksheets to implement
the following set of functions using a ROM, a PLA and a PAL. That
is, use a ROM to implement all three functions, then a PLA to implement all
three, and finally a PAL. For the PLA, try to reduce the number of
AND gates you have to program.
Make sure you identify your solutions.
f1 = y'z + w'z
f2 = w'xy' + wy'z + wx'y + x'yz'
f3 = xyz' + wx'z
2. (25 points) Use the ROM, PLA and PAL worksheets to implement
the following set of functions, represented using the SOP shorthand. Again
for the PLA, try to reduce the number of AND gates you program. Use
the same ROM worksheet as you used in #1. Why can't you use the same
PLA and PAL worksheets?
f1 = SUM m(1, 4, 5, 7, 13) + d(3, 6)
f2 = SUM m(3, 5, 7) + d(6)
f3 = SUM m(3, 4, 11, 13, 15) + d(9, 14)
3. (25 points) In this problem, you are to implement a function
that looks at 4 consecutive bits and detects whether it contains an unbroken
string of 1's. There are 7 cases: 0001, 0011, 0111, 1111, 1110, 1100,
1000.
a) Design this function using a ROM worksheet. Share the ROM from problems 1 and 2.4. (25 points) Using ActiveHDL, design and test an 8bit shifter circuit that implements the C/Java >> (arithmetic shift right) operation. The circuit has two inputs: an 8bit data input and a 3bit shift amount input. The output value is the input, shifted right by the shift amount. (This also implements divide by a power of 2.) Make sure your circuit works for both positive and negative numbers (2's complement) . You will find a test fixture in the class hw4 directory.
b) The PAL worksheet has 6 inputs. Generate 3 outputs, one for the first group of 4 bits, one for the second 4 bits and one for the last group of 4 bits.
c) The PLA worksheet also has 6 inputs. Generate 3 outputs as you did for part (b). Try to minimize the number of AND gates that you program.
5. [Extra credit  25 points] (This is a challenge for
those who have extra time.)
Use ActiveHDL to design and test a Logic Unit that computes an arbitrary
bitwise logic function, as indicated by a 4bit opcode, on two 8bit
numbers. Each bit of the result is formed by applying the logic function
to the corresponding pair of bits of the inputs. Implement this Logic
Unit using eight 41 multiplexors.
The following table defines the functions you are to implement and
gives an example of each using 4bit numbers. Part of the design procedure
is to assign the opcode values. You will find a test fixture in the
class hw4 directory, but you will have to modify it based on the opcodes
you have chosen.
(Hint: Don't use any other components
except the eight 41 multiplexors!)
Function

C assignment 
If A = 1100, B = 0110, then C = 
Zero 
C = 0 
0000 
One 
C = 255 
1111 
OR 
C = A  B 
1110 
AND 
C = A & B 
0100 
XOR 
C = A ^ B 
1010 
EQUAL 
C = ~(A ^ B) 
0100 
A 
C = A 
1100 
B 
C = B 
0110 
NOT A 
C = ~A 
0011 
NOT B 
C = ~B 
1001 
NOR 
C = ~(A  B) 
0001 
NAND 
C = ~(A & B) 
1011 
B mask A 
C = ~A & B 
1000 
A mask B 
C = A & ~B 
0010 
B > A 
C = A  ~B 
1101 
A > B 
C = ~A  B 
0111 