INTERNAL ARTECHITURE OF 8051 MICROCONTROLLER

 Architecture of 8051 microcontroller 

Oscillator and clock generator 

All operations in a micro controller by the help of and oscillator clock. The oscillator click pulse generated to pulses by which all internal operations.a resonant network connected through the PIN XTA1 and XTA2 form up ab oscillator. For this purpose a quartz crystal and capacitor are employed.

ALU

It is 8 bit unit.it performs logical operations like AND,OR,XOR. It manipulates 8 bit and 16 bit data .it calculated address of jump locations in relative branch instructions. It performs compare,rotate,and complement operations.it consist of boolean processor which perform bit,set,test,clear,and complement 8051 microcontroller consist 3 of general purpose registers.  and two of them are called "math registers". A and B and 32 are "bank of registers".

ACCUMULATOR A REGISTER 

It consist of 8 bit register .it address is EOH and it is bit and byte accesable results of arithmetic and logical operations performed by ALU is accumulator located by this register.therfore it is called accumulator register.it is used to store 8 bit data and to hold one of operand of ALU units.

B REGISTER

It is special 8 bit math registers.it is bit and byte accessible. It is used in consumption with a registers. It is used as general purpose registers to store 8 bit data.

PSW(PROCESSOR STATUS WORD)

It is 8 bit register.it is address is DOH.and it is bit and byte accessible. It has four conditions of flags and three control flag.

Conditional flags are

1. Carry flag

This are additional and subtraction any carry or barrow is generated they carry flag is set other wise carry flag is reset. It is used in arthimetic logical jump, rotate operations. 

2. Auxiliary  carry flag

It is addition and subtraction any carry or barrow is generated from lower four bit to higher four bit them AC sets else .it reset.

3.overflow flag

It is signed arithmetic operations results exists more than 7 bits than or flag sets else resets.

4.parity flag

It is in results even under of one's are present then .it is called even Parity and Parity flag.

CONTROL FLAGS

1.FO

It isdefined flag .they are used to define the function of this flag.the user can set,test,clear.this flag through software. 

2.RS1 AND RS0

 These are flags are used to select bank of registers by resetting those flags

PROGRAM COUNTER

The program counter is a two byte address.which tells the 8051 where next instruction to execute is found in memory.

DPTR(DATA POINTER REGISTER)

It is a 16 bit register used to hold the address of external ram where data is stored.it is store 16 bit data .it is divided into  two 8 bits 

They are

1.data pointer higher

2.data pointer lower