MICROCONTROLLERS

The morning sessiuon was handled by Bejoy sir, on microcontrollers.


A microcontroller (sometimes abbreviated µC) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals.It is designed to carry on a particular function where as a microprocessor is for a general purpose.Before inputting something care should be taken that  a 1 should be given to the D flipflop to make the transistor in the OFF state.


DELAY GENERATION
There are two methods for delay generation which are:

1. LOOP Technique.
2. Using Timer.

LOOP TECHNIQUE: This is very simple software based delay technique. In this method we load a number in a RAM location and decrement it till it becomes Zero.

USING TIMER: Many times we require precise internal time delays between two actions this can be accomplished using software techniques like Loop Technique but these delays keep the processor occupied because of which other important functions cannot be done. To relieve the processor of this burden we can use TIMERS provided by the controller. 8051 has two internal timers T0 and T1.

The timers count increments by every MACHINE CYCLE. A single Machine Cycle consists of 12 crystal pulses. i.e.
1 MACHINE CYCLE = Crystal Time/12.
Crystal Time = 1/Crystal Frequency.
So if we use 12MHz crystal then the timer will increment by 1 in every 1µS. The Timer always COUNTS UP, doesn’t matter in which mode it is being used the timer value is always incremented


INTERRUPT AND POLLING:

In a computer, a polled interrupt is that which notifies the part of the computer containing the I/O interface that a device is ready to be read or otherwise handled but does not indicate which device. The interrupt controller must poll (send a signal out to) each device to determine which one made the request.


An interrupt is considered to be an emergency signal that may be serviced. The Microprocessor may respond to it as soon as possibleIt is of two types:
1.VECTORED: The address of the subroutine is already known to the Microprocessor.
2.-NON VECTORED: The device will have to supply the address of the subroutine to the Microprocessor.


What happens when MP is interrupted ?
When the Microprocessor receives an interrupt signal, it suspends the currently executing program and jumps to an Interrupt Service Routine (ISR) to respond to the incoming interrupt. Each interrupt will most probably have its own ISR.ISR is an interrupt service routine is a software routine that hardware invokes in response to an interrupt. ISRs examine an interrupt and determine how to handle it.


SERAIL AND PARALLEL COMMUNICATION:
Serial communication is the process of sending data one bit at a time, sequentially, over a channel or computer bus.
Parallel communication is a method of sending several data signals simultaneously over several parallel channels. 

A Frame is a digital data transmission unit or data packet that includes a sequence of bits or symbols making it possible for the receiver to detect the beginning and end of the packet in the stream of symbols or bits. 
Asynchronous transmission uses start and stop bits to signify the beginning bit.Synchronous transmission uses no start and stop bits, but instead synchronizes transmission speeds at both the receiving and sending end of the transmission using clock.Simplex communication refers to communication that occurs in one direction only(radio).A half-duplex (HDX) system provides communication in both directions, but only one direction at a time (not simultaneously,"walkie-talkie").A Duplex communication system is a point-to-point system composed of two connected parties or devices that can communicate with one another in both directions simultaneously. An example of a duplex device is a telephone.

The second sesion was on the practical use of what we studied in the morning.We were divided into two groups consisting of four members each and the design and programming using arduino  duemilanove  was explained.The lighting of an LED with and without a push button switch was performed.

The Arduino Duemilanove ("2009") is a microcontroller board based on the ATmega168  or ATmega328 . It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.
"Duemilanove" means 2009 in Italian and is named after the year of its release.

  

Arduino hardware is programmed using a Wiring-based language (syntax and libraries), similar to C++ with some simplifications and modifications, and a Processing-based integrated development environment.