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Main points of this exam paper are: Clock Inputs, Transparent Latches, Basic Gates, Toggle Enable Input, Six Counter, Multi-Digit Systems, Datapath Elements, Computer Engineering, Function Code, Logical Function
Typology: Exams
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4 problems, 5 pages Exam Three 8 April 2009
Instructions: This is a closed book, closed note exam. Calculators are not permitted. If you have a question, raise your hand and I will come to you. Please work the exam in pencil and do not separate the pages of the exam. For maximum credit, show your work. Good Luck!
Your Name ( please print ) ________________________________________________
1 2 3 4 total
4 problems, 5 pages Exam Three 8 April 2009
Problem 1 (2 parts, 24 points) Counters
Part A (12 points) Design a toggle cell using transparent latches and basic gates. Use an icon for the latch. Your toggle cell should have an active high toggle enable input TE , and an active low clear input CLR¯¯¯ , clock inputs Φ 1 and Φ 2 , and an output Out. The CLR¯¯¯ signal has precedence over TE. Label all signals. Also complete the behavior table for the toggle cell.
Out
TE CLR¯¯¯ CLK Out
0 0 ↑↓
1 0 ↑↓
0 1 ↑↓
1 1 ↑↓
Part B (12 points) Now combine these toggle cells to build a divide by six counter. Your counter should have an external clear, external count enable, and three count outputs O 2 , O 1 , O 0. Use any basic gates (AND, OR, NAND, NOR, & NOT) you require. Assume clock inputs to the toggle cells are already connected. Your design should support multi-digit systems.
Ext Clr
Ext CE TE Out Clr
TE Out Clr
TE Out Clr
4 problems, 5 pages Exam Three 8 April 2009
shown here. Use a decoder if necessary. Place a star on the chip(s) that contain address 26,000,000.
ADDR
MSEL
D D D D
8M x 4
D D D D
ADDR
CS
8M x 4
D D D D
ADDR
CS
8M x 4
D D D D
ADDR
CS
8M x 4
D D D D
ADDR
CS
8M x 4
D D D D
ADDR
CS
8M x 4
D D D D
ADDR
CS
4 problems, 5 pages Exam Three 8 April 2009
Problem 4 (2 parts, 28 points) Microcode
Using the supplied datapath, write microcode fragments to accomplish the following procedures. Express all values in hexadecimal notation. Use ‘X’ when a value is don’t cared. For maximum credit, complete the description field.
Part A (14 points) (^7 ) 16
= Modify only R5, R 6 and R 7.
# X Y Z rwe imen im va auen -a/s luen lf suen st lden enst r/-w msel description
1 2 3 4 5 6 7
Part B (14 points) Write a microcode sequence that loads a 32 bit word from memory location 0x4000, unpacks and averages two 15 bit unsigned values (A and B), and then stores the result back to memory location 0x4000. Assume the most significant two bits of the register are zero. Modify only R 1 , R 2 , and R 3.
0 0 A B 31 30 29 15 14 0
# X Y Z rwe imen im va auen -a/s luen lf suen st lden enst r/-w msel description
1 2 3 4 5 6 7 8
