PIC 16F84A

The PIC16F84A is an 8-bit microcontroller of RISC (Reduced Instruction Set Computer) architecture. It uses a total number of 35  instructions. It has a total of 18 pins and is mostly found in a DIP18 type of case. The specifications are as follows:

1.Flash Memory (1KB) : For storing a program. It can be erased and rewritten almost 1000 times.

2.EEPROM (64 bytes) - Usually used for storing important data that will be secure even in power failure.

3.RAM - Memory used by a program to store temporary data during its execution.

4.CENTRAL PROCESSING UNIT-  It coordinates the work  and executes the user program.

5.PORTS- There are two ports portA(5 bits) and portB(8 bits). These 13 pins can be configured as input/output.

        Pin Configuration                                                                PIC 16F84A in reality

              Vss - Ground  | V_DD - Positive |  RA0  to  RA4 - Port A |  RB0  to  RB7 - Port B | MCLR - Master Clear

Block Diagram - Internal Structure of PIC

A Sample Program for PIC 16F84A microcontroller.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Author : Eby P.Kurien
; Date : 25/10/2006
; Version: 1.0
; Title: PIC16F84A : Use of TRIS (Beware! some PICs does not support this inst.) & MOVLW instruction
; Description: Make bit 0 & 3 of port B high.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


              Processor PIC16F84A                                                       ;Tell which processor we are using
              include<p16f84a.inc>                                                         ; Include its default values
             __config _XT_OSC & _PWRTE_OFF & _WDT_OFF    ; Cofiguration of fuses

             org 00h                                 ;Reset vector/Where to start
             movlw b'00000000'              ;move binary 0 to W register
             tris portb                              ;Make all pins of portb as output 
             movlw b'00001001'              ;move binary 00001001 to W register 
            movwf portb                          ;move the same to port B / bits 0 & 3 will go high 
loop:    goto loop                               ;endless loop
            end                                        ;end of the program(for the assembler)

Copy the program to notepad and assemble it using MPASM from Microchip.The result is the following HEX file

:020000040000FA
:0A0000000030660009308600042875
:02400E00F93F78
:00000001FF

Use the HEX file and program the PIC using a suitable programmer and software.