Serial Communication in 8051 Micro-controller
Micro-controllers need
to communicate with external devices such as sensors, computers and so on to
collect data for further processing. Data communication generally done by means
of two methods:
1.
Parallel
data transfer and
2.
Serial data
transfer
Parallel data transfer
|
Serial data transfer
|
|
 |
8
data lines are needed to transfer a byte of data.
|
1
data lines are needed to transfer a byte of data.
|
8
bit data is transferred at a time
|
Only
1 bit data is transferred at a time
|
Time
required to transfer the data is less.
|
Time
required to transfer the data is more.
|
Data
transfer is fast
|
Data
transfer is slow.
|
More
advantageous over small distance.
|
More
advantageous over long distance.
|
Cost
of connecting two distance point is high for long distance.
|
Cost
of connecting two distance point is low for long distance.
|
Fig.
Transfer of data serially
A.
Types of
communication
The communication links are classified on the basis
of transmission: 1)
Simplex and 2) Duplex
1 1)
Simplex:
·
The simplex is one way transmission.
·
The data
will be transmitted only in one direction
2 2)
Duplex
·
The simplex is two way transmissions.
·
Half
Duplex: Half duplex means data will be
transmitted in both directions but at one time, only one device can transmit.
This means that the line has to turn around after communication is complete in
one direction.
· Full
Duplex: full duplex means data may be
transmitted in both directions at one time, while one device is transmitting,
it can also receive data transmitted from other device at same time.
The
transmitter and receiver are configured to communicate at some data transfer
rate before communication starts. This data transfer rate or number of bits
transmitted per second is called baud rate for handling serial communication.
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