“In
this blog we will discussed about wired communication modules in
microcontroller, types of communications such as parallel, serial, synchronous
or asynchronous communication.”
Main
function of communication modules in microcontroller is for interacting with
other microcontroller, peripherals, PC or other modules. These communications
modules are inbuilt in microcontrollers. Communication protocols are the rules
and regulation which both devices follow to communicate with each other. For
example if two microcontrollers wants to communicates with UART it requires
that both microcontroller should configure for same baud rate, no of stop bits
and data bit to be communicated.
Parallel Communication
In
parallel communication two devices communicates through several lines by
communicating more than one bit at a time. In parallel communication
transmitter will uses serial in and parallel out shift registers. The receive
data can be directly read through 8-bit GPIO Register.
Parallel
communication used for short distance communication. Example of parallel
communication can be found in LCD interfacing through microcontroller. Parallel
communication requires large numbers of electrical conductors wires and
expensive to setup it. In parallel communication number of conductor wires
increases as increase in numbers of bits to be transmitted at one time.
Serial Communication
In
serial communication two devices communicates through single wire by
communicating single bit at a time. Data
bits are transferred sequentially. At transmitter side there will be a parallel
in serial out shift register and at receiver there will be serial in parallel
out shift register. In serial
communication data is communicated in packet format by adding start and stop
bits in the data.
Data
is transmitted from one device to another device through single electrical
conductor. Serial communication used in long distance communication and less
expensive then parallel communication. Examples of serial communications
protocol are as UART, USARTSPI, and I2C etc.
If
both Serial and parallel channels for 1-byte communication are operated on same
clock than Parallel communication speed will be 8 time faster than serial
communication.
Serial
communication can be Synchronous or Asynchronous.
Synchronous
communication
In
Synchronous communication transmitter and receiver work on the same clock
signal. This clock signal is provided by
the master device who initiates the communication. Receiver will detect the data according to
timing of clock signal. Data transfer rate in Synchronous communication is
faster as compare to asynchronous communication.
In
synchronous communication there will be one master device and all devices are
slave device. To start communication master will first generate start
communication frame. In synchronous communication all the slave devices are
addressed or selected through control signal from master device. Example of
Synchronous communication protocols are SPI and I2C.
Asynchronous
Communication
In
asynchronous communication there is common clock signal between transmitter and
receiver. To start communication it is required that sender and receiver should
be configured on the same communication parameters such and data communication
speed etc. In asynchronous communication bits are grouped together and control
bit such as Start and stop bit also added with data to be transfer. To properly
receives data receiver will oversampling the data.
Asynchronous
communication is slow due to increase in extra control bit with every byte of
data. If we are transmitting 8 bit data with two control bit start and stop
bits than there will be 25% overhead. Example
of asynchronous communication is UART.
Continued...........
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