31. Communication methods

Question 1

what is data communication?

Answer 1

Sending and or receiving data from one device to another.

Takes place internally within the device also, the CPU and its peripheral devices via busses

Question 2

What are the 2 main types of data transmission?

Answer 2

Serial data transmission

Parallel data transmission

Question 3

What is serial data transmission?

Answer 3

Bits of data are sent 1 at a time over a single wire

Question 4

How can high data transfer speeds be achieved during serial data transmission?

Answer 4

Use of fibre optic cables

Question 5

`What is parallel data transmission?

Answer 5

Bits of data are sent simultaneously over a number of parallel wires

Question 6

When is parallel data transmission most often used?

Answer 6

Integrated circuits and within RAM

Question 7

What are the disadvantages of serial data transmission?

Answer 7

Slower rate of transmission because data flows through a single line.
Half duplex, Data can travel in both directions but never at the same time.

Question 8

What are the advantages of serial data transmission?

Answer 8

Less errors and noise during transmission compared to parallel transmission
Reliable and straightforward.
Reliable over long distances due to singular wire

Question 9

What are the disadvantages of parallel data transmission?

Answer 9

Only reliable over very short distances as each wire has its own properties and so the speed of transmissions is very dependant on the wire it is travelling.
More errors and noise during transmission. - skew can occur if bits travel at slightly different speeds across the wires
Unreliable and complicated compared to serial transmission

Question 10

What are the advantages of parallel data transmission?

Answer 10

Faster because data flows through multiple lines.
Full duplex, data is able to travel in both directions at the same time.
Cables are thinner, longer and more economical

Question 11

What is speed of data transmission measured in?

Answer 11

BIT rate (bits per second)

Question 12

Define BAUD rate.

Answer 12

The rate at which a signal changes

Question 13

Define bandwidth

Answer 13

Range of frequencies that a transmission medium can carry.

usually expressed in bits per second (bps)

Question 14

What does a larger bandwidth equate to?

Answer 14

More data can be transmitted at a singular time

Question 15

define bit rate

Answer 15

the speed at which data is transmitted serially, measured in bits per second

Question 16

how do you calculate the bit rate of a channel?

Answer 16

baud rate x number of bits per signal

Question 17

define latency

Answer 17

latency is the time delay between the moment that transmission of the first byte or packet of a communication starts and when its received at its destination
primarily a function of how long it takes information to travel from source to destination

Question 18

define protocol

Answer 18

a set of rules relating to the communication between devices

Question 19

how is asynchronous transmission used?

Answer 19

one byte at a time is sent, with each character being preceded by a start bit and followed by a stop bit
the start bit alerts the receiving device and synchronises the clock inside the receiver ready to receive the character
the baud rate at the receiving end has to be set up the same as the senders baud rate or the signal will not be received correctly
the stop bit allows the the receiver the time to identify the next start bit and gives the receiver time to process the data before the next value is transmitted
a parity bit is usually also included as a check against incorrect transmission, thus for each character being sent a total of 10 bits is transmitted

Question 20

how is asynchronous transmission used?

Answer 20

one byte at a time is sent, with each character being preceded by a start bit and followed by a stop bit
the start bit alerts the receiving device and synchronises the clock inside the receiver ready to receive the character
the baud rate at the receiving end has to be set up the same as the senders baud rate or the signal will not be received correctly
the stop bit allows the the receiver the time to identify the next start bit and gives the receiver time to process the data before the next value is transmitted
a parity bit is usually also included as a check against incorrect transmission, thus for each character being sent a total of 10 bits is transmitted

Question 21

when is asynchronous transmission used and what is its main advantage?

Answer 21

Usually used by PC’s , is economical for relatively small amounts of data.
the main advantage is that there does not need to be a way of sharing the clock signal between the two devices

Question 22

why do we need protocols to be set up to allow communication

Answer 22

a standardised set of rules has been devised covering standard for physical connections, cabling, mode of transmission, speed, data format, error detection and correction
any pieces of equipments which use the same communication protocol can be linked together.