PIC16F84 Microcontroller

 

►Introduction

PIC16F84 belongs to a class of 8-bit microcontrollers of RISC architecture. Its general structure is shown on the following map representing basic blocks. Program memory (FLASH)- for storing a written program. Since memory  made in FLASH technology can be programmed and cleared more than once, it makes this microcontroller suitable for device development. EEPROM - data memory that needs to be saved when there is no supply. It is usually used for storing important data that must not be lost if power supply suddenly stops. For instance, one such data is an assigned temperature in temperature regulators.  If during a loss of power supply this data was lost, we would have to make the adjustment once again upon return of supply.

Thus our device looses on self-reliance. RAM - data memory used by a program during its execution. In RAM are stored all inter-results or temporary data during run-time. PORTA and PORTB are physical connections between the microcontroller and the outside world. Port A has five, and port B has eight pins. FREE-RUN TIMER is an 8-bit register inside a microcontroller that works independently of the program. On every fourth clock of the oscillator it increments its value until it reaches the maximum (255), and then it starts counting over again from zero. As we know the exact timing between each two increments of the timer contents, timer can be used for measuring time which is very useful with some devices. CENTRAL PROCESSING UNIT has a role of connective element between other blocks in the microcontroller. It coordinates the work of other blocks and executes the user program.

►Applications

PIC16F84 perfectly fits many uses, from automotive industries and controlling home appliances to industrial instruments, remote sensors, electrical door locks and safety devices. It is also ideal for smart cards as well as for battery supplied devices because of its low consumption.

EEPROM memory makes it easier to apply microcontrollers to devices where permanent storage of various parameters is needed (codes for transmitters, motor speed, receiver frequencies, etc.). Low cost, low consumption, easy handling and flexibility make PIC16F84 applicable even in areas where microcontrollers had not previously been considered (example: timer functions, interface replacement in larger systems, coprocessor applications, etc.).

In System Programmability of this chip (along with using only two pins in data transfer) makes possible the flexibility of a product, after assembling and testing have been completed. This capability can be used to create assembly-line production, to store calibration data available only after final testing, or it can be used to improve programs on finished products.

►Pin description

PIC16F84 has a total of 18 pins. It is most frequently found in a DIP18 type of case but can also be found in SMD case which is smaller from a DIP. DIP is an abbreviation for Dual In Package. SMD is an abbreviation for Surface Mount Devices suggesting that holes for pins to go through when mounting, aren't necessary in soldering this type of a component.

 

Pins on PIC16F84 microcontroller have the following meaning:

Pin no.1    RA2       Second pin on port A. Has no additional function.
Pin no.2    RA3       Third pin on port A. Has no additional function.
Pin no.3    RA4       Fourth pin on port A. TOCK1 which functions as a timer is also found on this pin. 
Pin no.4    MCLR    Reset input and Vpp programming voltage of a microcontroller.
Pin no.5    Vss        Ground of power supply.
Pin no.6    RB0       Zero pin on port B. Interrupt input is an additional function.
Pin no.7    RB1       First pin on port B. No additional function.
Pin no.8    RB2       Second pin on port B. No additional function. 
Pin no.9    RB3       Third pin on port B. No additional function. 
Pin no.10  RB4       Fourth pin on port B. No additional function.
Pin no.11  RB5       Fifth pin on port B. No additional function.
Pin no.12  RB6       Sixth pin on port B. 'Clock' line in program mode.
Pin no.13  RB7       Seventh pin on port B. 'Data' line in program mode.
Pin no.14  Vdd       Positive power supply pole.
Pin no.15  OSC2    Pin assigned for connecting with an oscillator.
Pin no.16  OSC1    Pin assigned for connecting with an oscillator.
Pin no.17  RA2      Second pin on port A. No additional function.
Pin no.18  RA1      First pin on port A. No additional function.

 

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