Information and Systems Flashcards
What defines something as analogue in nature?
- The signal can take any value and there are infinite possibilities
- The value of the signal varies with time
What defines something as digital in nature?
- Anything that deals in the realm of the discrete
- There is a limited set of values they can take
Define a bit
A binary digit
Define a byte
A sequence of 8 bits
Define a word
A sequence of N bits
What base is decimal?
Base-10
What base is binary?
Base-2
What base is hexadecimal?
Base-16
What does ADC stand for?
Analogue-to-digital converter
What is the role of an ADC?
To sample an analogue signal in order to produce a digital representation of the data in such a way that no important information is lost
State the Nyquist-Shannon Theorem
The sampling frequency must be at least two times the maximum frequency
In practice, what is the range of the sampling frequency?
Between two times and ten times the maximum frequency
Why is the Nyquist-Shannon Theorem used?
- Most signals consist of a mix of frequencies
- So, twice the max frequency ensures it is captured
What happens when sampling below the Nyquist rate?
Signal information is lost meaning received signal will appear lower than original signal
Define ADC resolution
The smallest voltage that can be represented digitally
How do you calculate resolution?
Voltage range/N - 1
How finely will an 8-bit ADC digitise a signal that occupies a voltage range of 0V to 5V?
- 2⁸ = 256
- 5/256-1 = 0.02V or 20mV
What is combination logic?
- In a circuit, output depends only on combination of its inputs
- Output is not influenced by previous inputs
- Circuit has no memory
What are the typical applications of combination logic?
- Data transfer circuits: control logic flow around a system
- Data processing circuits: process/transform data
How can data circuits be described?
- Truth table
- Boolean expression
- Circuit diagram
- Timing diagram
What type of Boolean expressions can’t be obtained from a truth table?
Expressions in minimised form
When can Boolean expression not be obtained from a truth table?
Never, they always can be obtained