What is PIC Microcontroller ? PIC Microcontroller Architecture, Working and Application

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PIC MICROCONTROLLERS

INTRODUCTION:

  • It is created by microchip technology which originated from the PIC160.
  • The early versions of PIC had only a Read only memory and Erasable Programmable Read only memory.
  • The abbreviation originally stood  for Peripheral interface controller but was later changed to Programmable intelligent computers.
  • These PICS were introduced in 1975 for the sole purpose of off-loading Input/Output tasks from the CPU in order to enhance the efficiency of the processor.

FEATURES:

 

  • Low cost.
  • Wide availability.
  • Different communication protocols are compatible such as:-

 

 

1.CAN

2.I2C

3.UART(Universal Asynchronous Receiver transmitter)

4.USB(UNIVERSAL SERIAL BUS)

CORE ARCHITECTURE:
  • Harvard architecture is employed here in this family.
COMPONENTS:

 

1.) DRAM(DATA MEMORY):

  • The PIC family comprises of a special registers that function as general purpose RAM.
  • These devices are employed with have banking mechanisms in order to extend memory.
  • An important point to note is that the external memory is not addressable.

   2.) CODESPACE:

  • There exists no facilities for the provision of external memory in the absence of such module.
  • Therefore usually the memory storage takes place on the following:-
    • ROM
    • PROM
    • EPROM

Exceptions: – PIC18  and PIC17.

   3.) WORD SIZE:

  • Program memory is usually implemented in single word instructions instead of bytes.
  • The addresses are handled in 8-bit format by these PIC microcontroller.
  • PIC 12 and PIC 16 have addresses of the same size as the instruction width size.
  • PIC 18 has address memory size as 8-bit increments which differs from instruction width of 16 bits.

    4.) STACKS:

  • Generally the PIC devices had a hardware module known as cell stack for the sole purpose of  storing return addresses.
  • The stacks present in the earlier versions was not accessible for software editing.
  • However the latest one PIC 18 has enabled software editing for the stack hardware module.

    5.) INSTRUCTION SET

  • Te Programmable intelligent controllers(low end ) has 35 bit instructions.
  • Whereas the high end one’s have over 80 instruction sets.
ADVANTAGES:-
  1. Reduced instruction set(RISC).
  2. Internally embedded oscillator with tunable speeds.
  3. Inexpensive microcontrollers.
  4. The wide availability of Dual inline Packages which makes it convenient for usage
LIMITATIONS:
  • Unfortunately only a single accumulator is available.
  • Operations and registers are not repetitive implying that sometimes single.
  • The cell stacks that are software programmed  will not be that efficient for addressing memory.

PAGED PROGRAM MEMORY:

  • We have two separate page memories pose a problem.
  • One is known s CALL whereas the other one is called GOTO(usually implemented in lookup tables)
  • They both comprise of 11 addressing bits so the page is 2048 instruction words.

BOOTLOADING:

  • Most of the modern flash based PIC’s can self-program itself.However there exists an alternative solution for programming.
  • The bootloader firmware enables the user to load on the PIC microchip using  The Inline serial port in conjunction with specific program software.

ADVANTAGES OF BOOTLOADER:

  • Quicker programming when compared to ICSP programming.
  • On the spot execution along with programming.
  • Programming and debugging can both be done using the same cable.

HARDWARE FEATURES:

1.EEPROM

2.Flash features

3.Watchdog timer

4.Sleeping modee

5.Various oscillator crystal configurations.

DEVICE PROGRAMMERS:

  • These devices are used to feed the program coding into the PIC chip.
  • Some of the famous programmers/ debuggers are:-
  1. MPLAB ICE
  2. MPLAB ICD4

In circuit emulators:

  • MPLABICE2000 is an example of a  full circuit emulators.
  • These tools are used in conjunction with the debuggers previously mentioned above for source level of target code.

PERFORMANCE:

  • Speed to cost ratio maximized here.
  • The  latency of interrupts is constant at three instruction cycles.
  • Timing and the design of microcircuit are efficiently saved.
  • The peculiar feature is that by default all the internal interrupts are already synchronized whereas the external interrupts have to be produced simultaneously with the four input clock cycles.

APPLICATIONS:

In most modern devices such as:-

  1. Mobile phones
  2. Vehicle systems
  3. Aerospace mechanisms