Digital Systems test

Question 1

When dealing with complexity, what does it mean? Abstraction

Answer 1

Make assumptions to simplify design; refine models as a design proceeds

Question 2

When dealing with complexity, what does it mean? Discipline

Answer 2

Restricts design choices

Question 3

When dealing with complexity, what does it mean? Hierarchy

Answer 3

Break systems into modules and sub-modules

Question 4

When dealing with complexity, what does it mean? Modularity

Answer 4

Give Modules a well-defined interface without side effects

Question 5

When dealing with complexity, what does it mean? Regularity

Answer 5

Minimise the number of different modules, reuse modules and repeat them in regular patterns where possible

Question 6

What are some examples of Non-recurring costs?

Answer 6

• non-recurring engineering
• manufacturing tool-up

Question 7

What are some examples of Recurring costs?

Answer 7

• raw-materials
• manufacturing
• service

Question 8

You are engaged to design a web site. Suggest ways in which you could take advantage of hierarchy, modularity, regularity and discipline

Answer 8

• Hierachy: organise content into pages and sub pages
• Modularity: helper scripts, modular with defined interface
• Regularity: Consistent page structure - reuse code, consistent look
• Disipline: Limit the number of fonts and avoid depreciated HTML tags

Question 9

Draw an NoR gate

Answer 9

Question 10

Draw an XoR gate

Answer 10

Question 11

How many bits of information are contained in the current state of a traffic light (red, amber or green)?

Answer 11

3 states bits of info: log₂ 3 = log 3/ log 2 = 1.585 bits

Need 2 bits to represent

Question 12

convert ABC to binary

Answer 12

1010 1011 1100

Question 13

convert 1011 0001 1010 to Hexadecimal

Answer 13

B1A

Question 14

assign y = s ? d1 : d0;

What does this mean?

Answer 14

// d1 if s is true, d0 if s is false

Question 15

What are Sum-of-producs and Product-of-sums in terms of truth tables

Answer 15

• Sum-of-products are the min terms for Y=1 where Y is the output
• Product-of-sums are the max terms for Y=0 where Y is the output

Question 16

State De Morgan’s theorem

Answer 16

Question 17

output reg y

Why was y declared with reg?

Answer 17

Because Y will undergo the always @ (*) function

Question 18

Write a 2:1 Mux truth table and a logic gate circuit

Answer 18

Question 19

Whats the difference between a logic circuit and a logic gate circuit

Answer 19

Logic circuit can be expressed as an and/or circuit which simplifies things. Logic gate circuit needs to have all gates to express the circuit in it’s full potential.

Question 20

Answer 20