Specifications

Chapter 2 - Microcontroller PIC16F84
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CHAPTER 2
Microcontroller PIC16F84
Introduction
CISC, RISC
Applications
Clock/instruction cycle
Pipelining
Pin description
2.1 Clock generator - oscillator
2.2 Reset
2.3 Central processing unit
2.4 Ports
2.5 Memory organization
2.6 Interrupts
2.7 Free timer TMR0
2.8 EEPROM Data memory
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 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
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