Tuesday, September 6, 2016

1.2.1 Data transmission


SHOW UNDERSTANDING OF WHAT IS MEANT BY TRANSMISSION OF DATA 
 
THE PHYSICAL TRANSFER OF DATA OVER A COMMUNICATIONS CHANNEL

DISTINGUISH BETWEEN SERIAL AND PARALLEL DATA TRANSMISSION
SERIAL DATA TRANSMISSION IS WHEN DATA IS SENT BIT BY BIT DOWN A SINGLE WIRE.
P
ARALLEL DATA TRANSMISSION IS WHEN DATA IS SENT DOWN MULTIPLE WIRES (NORMALLY 8 TO SENT A BYTE AT THE SAME TIME). 


DISTINGUISH BETWEEN SIMPLEX, DUPLEX AND HALF-DUPLEX DATA TRANSMISSION
SIMPLEX DATA TRANSMISSION CAN ONLY TRANSFER DATA IN ONE DIRECTION ONLY (BROADCAST RADIO).
H
ALF-DUPLEX DATA TRANSMISSION CAN TRANSFER DATA IN TWO DIRECTIONS BUT NOT AT THE SAME TIME (WALKIE-TALKIE). FULL-DUPLEX DATA TRANSMISSION CAN TRANSFER DATA IN TWO DIRECTIONS AT THE SAME TIME (PHONE). 


SHOW UNDERSTANDING OF THE REASONS FOR CHOOSING SERIAL OR PARALLEL DATA TRANSMISSION
Advantages (Serial)
Disadvantages (Serial)
Advantages (Parallel)
Disadvantages (Parallel)
Cheaper
Takes longer time to send data (over long periods of time)
Faster, more data sent at once
Interference, problem over long distance
Fewer Wires


More complicated transmission
Less complicated transmission


More expensive because more wires

SHOW UNDERSTANDING OF THE NEED TO CHECK FOR ERRORS
AS THERE MIGHT BE INTERFERENCE AND OTHER ERRORS WHICH MIGHT AFFECT THE DATA BEING SENT, AND NOBODY WANTS DATA THAT IS CORRUPTED AND CANNOT BE VIEWED


EXPLAIN HOW PARITY BITS ARE USED FOR ERROR DETECTION

PARITY CHECKS THE NUMBER OF 1’S IN A STRING OF DATA. THERE ARE TWO TYPES OF PARITY CHECK, EVEN AND ODD PARITY. BEFORE THE DATA IS SENT BETWEEN TWO COMPUTERS, A RULE IS SET; EVEN OR ODD PARITY. IF IT IS EVEN PARITY, THERE HAS TO BE A EVEN NUMBER OF 1’S IN THE DATA, IF IT IS ODD PARITY, THERE HAS TO BE A ODD NUMBER OF 1’S IN THE DATA. BEFORE THE DATA IS SENT, IF THE RULE IS EVEN PARITY, AND THE DATA ABOUT TO BE SENT HAS AN ODD NUMBER OF 1’S A 1 IS ADDED (THIS IS KNOWN AS THE PARITY BIT). IF THE RULE IS EVEN PARITY AND THE DATA ABOUT TO BE SENT HAS AN EVEN NUMBER OF 1’S, A 0 S ADDED. THIS ALSO APPLIES THE ODD PARITY RULE.

SHOW UNDERSTANDING OF THE USE OF SERIAL AND PARALLEL DATA TRANSMISSION, IN UNIVERSAL SERIAL BUS (USB) AND INTEGRATED CIRCUIT (IC)
Serial Uses
Parallel Uses
USB
CPU Connection
FireWire
ATA/IDE
Ethernet

Telephone Wire

PCI-E

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