The data
communication in Microprocessor is of two types i.e. Serial data communication
and parallel data communication.
1.Serial
data communication:
The data with in the micro
computer is transferred by parallel data, by using parallel data n bits are
transferred at a time. It is the fastest process but not applicable for long
distances due to requirement of n wires.
* To avoid
this, serial data communication is preferred for long distance because in
serial data only one bit transfer at a time through a single wire, so n bit
transfer made using single wire hence the cost us cheap
* The only
disadvantage of this process is slow data transmission compared with parallel
data transmission.
* Serial data
communication is of two types
1.Synchronous
serial data
2.Asynchronous
serial data
Synchronous serial data
|
Asynchronous serial data
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*The operating clock frequency of transmitter and
receiver is similar (FT = FR )
|
*The operating clock frequency of transmitter and
receiver is not similar (FT = FR )
|
*The error occur in data transmission are due to
slight frequency difference
|
*The slight difference in frequency of transmitter
and receiver which can be adjusted by using stop bits after each character is
transferred
|
*This type of data transfer is used in
Microprocessor and input, output devices matches in speed.
|
*This type of data transfer does not matches with
speed
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*The readiness for data transfer is not checked in
input and output devices.
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*The readiness for data transfer is checked by CPU.
|
Example: Data transfer between
processor and CRT terminal, key board, printer etc.
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Example: Data transfer between processor and modem, audio
cassettes etc..
|
Serial
data transmission standards:
The serial data communication
consists of some standards from which the data is to be transmitted from place
to place.
i)RS-232C:
It is manufactured by EIA (
Electronic Industries Association) mostly used for PC `s for serial data communication
up to the range of 50 feet.
* RS-232C
also reffered as single ended single wire communication.
ii)RS-422:
RS-422 is the updated version of
RS-232C. It fits well in process control applications up to the range of 4000
feet with data rate of 100kbps and for short runs 10Mbps maximum data rate.
* RS-422
referred as half dublex single source multi drop network.
iii)RS-485:
RS-485 and RS-422 are similar in
data rate and distance specifications but the differences is RS-485 has
multiple drives on same bus and provides bidirectional half dublex multi point
data communication.
2.Parallel
data communication:
In parallel data transmission the n bits
of data is transferred at a time but in short distance range. The n wires are
required to transfer n bits of data.
* The wire
used for parallel data communication rise to several problems like skew etc..
So the microcontroller and microprocessor are using serial data communication,
the applications of parallel data communication are used in CPU.
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