Data Transmission

Serial and ParallelTransmission

What is meant by transmission of data?• The movement of data in the form of bits between two devices

▪ From one computer to another

▪ From keyboard to CPU

▪ From CPU to printer

•Bits are sent as electric signals▪Presence of electricity = ON = 1

▪Absence of electricity = OFF = 0

•Data travels through a transmission media - usually cables or wires.

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Data Transmission Methods

Two methods :

1. Serial data transmission

2. Parallel data transmission.

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Serial data transmission Data is transmitted

•One bit at a time

•Along a single wire.

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Serial data transmission Benefits

• Single wire means there is less chance of interference or data

corruption

• Single wire means it is less expensive

• More reliable for sending data over long distances

• No problem of data synchronization at destination (Bits are in order)

Drawback

• Data is transmitted at a slower rate than parallel data transmission.

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Uses of serial data transmission

▪Connecting a device to the computer using a

USB port

▪Connecting the computer to a modem

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USB• USB means Universal Serial Bus

• Uses serial data transmission method

• It has become the standard method for

transferring data between a computer and a

number of devices.

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Benefits of using USB connections betweena computer and a device

• Devices are automatically detected when connected for the first time

• The connector only fits one way so impossible to connect a device

incorrectly

• Has become the industry standard – nearly all devices use USB

• Supported by many operating systems – Windows, Apple, Android …

• Faster transmission speed compared to wireless.

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Textbook -USB Benefits and drawbacks▪From text book – read page 16

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Parallel data transmissionData is transmitted:

•Multiple bits at a time •On separate lines

To transmit 1 byte (8 bits) , we will need 8 wires

To transmit n bits, we will need n wires.

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Parallel data transmissionBenefits:

• Faster than serial transmission

• Suitable for transmission over short distances

Drawback:

•Uses more wires, hence more costly than serial transmission

• Over longer distances, the bits may no longer be synchronized

(bits are received in the wrong order).

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Uses of parallel data transmission• Sending data from a computer to a printer

• Internal data transfer

▪Between the CPU and memory

▪Data transfer inside Integrated circuits, buses and other internal

components

▪ Because:

▪Data travels very small distances

▪High transmission speed is achieved.

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Choosing between serial or parallel transmissionWe need to consider the following:

1. Distance from sender to receiver

• Which one to choose when distance is short/long?

2. Transmission speed

▪ Which one offers higher transmission speed?

3. Cost

▪ Which type of transmission costs less?

4. Reliability

▪ Which transmission type is more reliable (less errors)?

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Homework 1

1. Computer Science Workbook

• Page 13 Q 2

• Page 14 Q 3 (a) , (b) , (c)

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Homework 12. (a) Explain what is meant by:

(i) Serial data transmission

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(ii) Parallel data transmission

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(b) A computer in a factory is connected to a printer. The printer is located in an office 1 km away from the factory.

Identify which data transmission method would be most suitable for this connection.

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Give two reasons for your choice.

1 ................................................................................................................................................

2 ................................................................................................................................................

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