Explain serial and parallel communication
Serial and Parallel Communication
SERIAL
Serial communication is the method of transferring one bit at a time
through a medium.
Serial transmission is much more common, particularly over longer distances. It is generally much cheaper as only a single channel between sender and receiver is required, eg: The seven bits (plus one parity check bit) making up an American Standard Code for Information Interchange (ASCII) character are transmitted serially in sequence by the sender and are reassembled into the character by the receiver. A common example of a serial interface
standard is Recommended Standard 232 (RS232).
Three things should be considered when discussing serial communications and the equipment to carry this out:
Electrical standards associated with the interface
Mechanical standards associated with the interface
Standards organisations involved
Data transmission may take place in one direction only or it may be bi-directional. There are 3 groups into which the channel can be classified:
asynchronous transmission:
With asynchronous transmission signal timing is not required; signals are sent in an agreed pattern of bits and if both ends are agreed on the pattern then communication can take place.
Bits are grouped together and consist of both data and control bits. If the signal is not synchronised the receiver will not be able to distinguish when the next group of bits will arrive. To overcome this the data is preceded by a start bit, usually binary 0, the byte is then sent and a stop bit or bits are added to the end. Each byte to be sent now incorporates extra control data. In addition to the control data small gaps are inserted between each chunk to distinguish each group.
In asynchronous transmission each bit remains timed in the usual way. Therefore, at bit level the transmission is still synchronous (timed). However, the asynchronous transmission is applied at byte level, once the receiver realises that there is a chunk of incoming data timing (synchronisation) takes place for the chunk of data.
Asynchronous transmission is relatively slow due to the increased number of bits and gaps. It is a cheap and effective form of serial transmission and is particularly suited for low speed connections such as keyboard and mouse.
One example of asynchronous transfer is Asynchronous Transfer Mode (ATM) switching. ATM allows voice, data and video to be transmitted in fixed length cells of 53 bytes.
PARALLEL
Parallel communication is the method of transferring blocks,
eg: BYTEs, of data at the same time.
Parallel transmission requires a separate channel for each bit to be transmitted. Therefore, to transfer a byte, eight channels will be required between the sender and receiver. Added to these eight are additional channels that are needed for control information and if full duplex communication is required then even more channels would be required. Parallel transmission is rare, other than for very short distances, eg: within a computer, eg: data bus, or between a computer and a printer, eg: Centronics printer interface.
1.6 define channel capacity.
ans:
Transmission Modes
ans:
Simplex
Half Duplex
Full Duplex
Baud and Data Rates
Serial and Parallel Communication
SERIAL
Serial communication is the method of transferring one bit at a time
through a medium.
Serial transmission is much more common, particularly over longer distances. It is generally much cheaper as only a single channel between sender and receiver is required, eg: The seven bits (plus one parity check bit) making up an American Standard Code for Information Interchange (ASCII) character are transmitted serially in sequence by the sender and are reassembled into the character by the receiver. A common example of a serial interface
standard is Recommended Standard 232 (RS232).
Three things should be considered when discussing serial communications and the equipment to carry this out:
Electrical standards associated with the interface
Mechanical standards associated with the interface
Standards organisations involved
Data transmission may take place in one direction only or it may be bi-directional. There are 3 groups into which the channel can be classified:
asynchronous transmission:
With asynchronous transmission signal timing is not required; signals are sent in an agreed pattern of bits and if both ends are agreed on the pattern then communication can take place.
Bits are grouped together and consist of both data and control bits. If the signal is not synchronised the receiver will not be able to distinguish when the next group of bits will arrive. To overcome this the data is preceded by a start bit, usually binary 0, the byte is then sent and a stop bit or bits are added to the end. Each byte to be sent now incorporates extra control data. In addition to the control data small gaps are inserted between each chunk to distinguish each group.
In asynchronous transmission each bit remains timed in the usual way. Therefore, at bit level the transmission is still synchronous (timed). However, the asynchronous transmission is applied at byte level, once the receiver realises that there is a chunk of incoming data timing (synchronisation) takes place for the chunk of data.
Asynchronous transmission is relatively slow due to the increased number of bits and gaps. It is a cheap and effective form of serial transmission and is particularly suited for low speed connections such as keyboard and mouse.
One example of asynchronous transfer is Asynchronous Transfer Mode (ATM) switching. ATM allows voice, data and video to be transmitted in fixed length cells of 53 bytes.
PARALLEL
Parallel communication is the method of transferring blocks,
eg: BYTEs, of data at the same time.
Parallel transmission requires a separate channel for each bit to be transmitted. Therefore, to transfer a byte, eight channels will be required between the sender and receiver. Added to these eight are additional channels that are needed for control information and if full duplex communication is required then even more channels would be required. Parallel transmission is rare, other than for very short distances, eg: within a computer, eg: data bus, or between a computer and a printer, eg: Centronics printer interface.
1.6 define channel capacity.
ans:
Transmission Modes
ans:
Simplex
Half Duplex
Full Duplex
Baud and Data Rates
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