- 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.
- Low cost.
- Wide availability.
- Different communication protocols are compatible such as:-
3.UART(Universal Asynchronous Receiver transmitter)
4.USB(UNIVERSAL SERIAL BUS)
- Harvard architecture is employed here in this family.
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.
- 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:-
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.
- 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.
- Reduced instruction set(RISC).
- Internally embedded oscillator with tunable speeds.
- Inexpensive microcontrollers.
- The wide availability of Dual inline Packages which makes it convenient for usage
- 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.
- 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.
5.Various oscillator crystal configurations.
- These devices are used to feed the program coding into the PIC chip.
- Some of the famous programmers/ debuggers are:-
- MPLAB ICE
- 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.
- 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.
In most modern devices such as:-
- Mobile phones
- Vehicle systems
- Aerospace mechanisms