Aum Amriteswaryai Namah:

HHHHave separate program memory and data Memory AAAAccessed by separate busses

PIC 16F877A Microcontroller Like any microcontroller, it has CPU, memory and I/O in one chip. Using some I/O devices like keypad, display and interfacing circuits we can create a ‘complete system’. PIC based wireless sensor board

Aum Amriteswaryai Namah:

PIN DIAGRAM

Memory Classification Memory Memory Program Memory Program Memory Data Memory Data Memory General Purpose RAM General Purpose RAM Special Function Registers Special Function Registers

Specifications of program memory PM (program memory) = 8k words PC (program counter = 13 bits wide to address PM) Each word = 14 bits => All op-codes are 14 bit wide. PM (program memory) = 8k words PC (program counter = 13 bits wide to address PM) Each word = 14 bits => All op-codes are 14 bit wide.

Data Memory Organization DDDData memory = RAM File = File Registers. 555512 bytes arranged in 4 banks of 128 bytes each.  W W W Width of word = 8 bits GGGGeneral Purpose Registers (GPR): Called scratch pad area/registers ----For data storage -----For scratch pad operations SSSSpecial Function Register (FSR, STATUS etc.) ----Control operation of the device

RAM FILE BANKS FFirst 32 of each bank = reserved. The important register (eg: STATUS) values are repeated in each bank. EEach bank = 128 bits wide. Hence need only 7 bits for address. To select one among the 4 banks, 2 bits (b6 b5) of status register is used. bb6 = RP1, b7 = RP0 RRP1 RP0 = 00 => bank 0 selected ; RP1 RP0 = 01 => bank 1 selected RRP1 RP0 = 10 => bank 2 selected ; RP1 RP0 = 11 => bank 3 selected

16 registers of each bank is common and repeated in all 4 banks. Hence common data is stored here during bank switching. RAM FILE BANKS contd… GPRs SFRsBank0000h 01Fh 020h 07Fh GPRs SFRs Bank1 080h 09Fh 0A0h 0FFh 0F0h GPRs SFRs Bank2 100h 11Fh 120h 17Fh 170h GPRs SFRs Bank3 180h 19Fh 1A0h 1FFh 1F0h RP RP RP RP RP RP RP RP = 00 = 01 = 10 = 11 = 00 = 01 = 10 = 11

WREG - Working Register TTTThe WREG register is referred to as working register IIIIs a special register inside the CPU of uC DDDDoesn’t reside in Data Memory like SFRs IIIInvolves in the execution of many instructions CCCCan be the destination of many instructions.

Status Register

Status Register contd..