Communication & Networking - A Level Comp Sci

What are the 2 main types of data transmission?

• Serial

• Parallel

How does serial transmission work? (+ what distances is it best for?)

Data is sent 1 bit at a time along 1 wire

• best for medium/long distance

How does parallel transmission work? (+ what distances is it best for?

Data is sent simultaneously down multiple wires at the same time

What is data skew in parallel transmission? (+why does it occur?)

The time delay between data from different wires reaching the receiver in parallel transmission

• due to slightly differing electrical properties between each wire/medium

Why is series better than parallel transmission? (4 reasons)

1. No data skew (only 1 wire) - more reliable

2. Cheaper to install (only 1 wire, less complex)

3. Less interference between wires (crosstalk) with use of shielded cables

4. Lower power consumption

What is synchronous transmission? (+ serial or parallel?)

Mostly parallel data transmission; can be serial

• data is sent at regular intervals using a clock signal shared between transmitter & receiver

When & where is synchronous data transmission used?

• Where? In control bus of a CPU

• When? during the fetch-execute cycle

What is asynchronous data transmission?

A method of serial data transmission;

• Data is sent as individual characters/bytes with start & stop bits to signal the beginning and end of transmission

When & where does asynchronous transmission occur?

• When? For small intermittently-sent data

• Where? In the computer’s communication ports for connecting peripherals

What is the purpose of a start bit in asynchronous transmission?

Signals the beginning of data packet/byte to the reciever’s clock

What is the purpose of a stop bit in asynchronous transmission?

Signals the end of a data packet/byte for the receiver to process the received data