8051 Microcontroller and 8085 microprocessor

 8051Microcontroller:

what is Microcontroller?

Microcontroller

A Microcontroller is a programmable digital processor with necessary peripherals.  Microcontrollers is a complex sequential digital circuits meant to carry out job according to the program / instructions. Sometimes analog input/output interface makes a part of microcontroller circuit of mixed mode (both analog and digital nature). A microcontroller can be compared to a Swiss knife with multiple functions incorporated in the same IC.

 Family of 8051microcontroller

                                                               8051 family has three member they are  8031,8052and 8051.

Different between Microprocessor and Microcontroller

Microprocessor	Microcontroller
Microprocessor is the heart of Computer system.	Micro Controller is the heart of an embedded system.
It is only a processor, so memory and I/O components need to be connected externally	Micro Controller has a processor along with internal memory and I/O components.
Memory and I/O has to be connected externally, so the circuit becomes large.	Memory and I/O are already present, and the internal circuit is small.
You can’t use it in compact systems	You can use it in compact systems.
Cost of the entire system is high	Cost of the entire system is low
Due to external components, the total power consumption is high. Therefore, it is not ideal for the devices running on stored power like batteries.	As external components are low, total power consumption is less. So it can be used with devices running on stored power like batteries.
Most of the microprocessors do not have power saving features.	Most of the microcontrollers offer power-saving mode.
It is mainly used in personal computers.	It is used mainly in a washing machine, MP3 players, and embedded systems.
Microprocessor has a smaller number of registers, so more operations are memory-based.	Microcontroller has more register. Hence the programs are easier to write.
Microprocessors are based on Von Neumann model	Micro controllers arc based on Harvard architecture
It is a central processing unit on a single silicon-based integrated chip.	It is a byproduct of the development of microprocessors with a CPU along with other peripherals.
It has no RAM, ROM, Input-Output units, timers, and other peripherals on the chip.	It has a CPU along with RAM, ROM, and other peripherals embedded on a single chip.
It uses an external bus to interface to RAM, ROM, and other peripherals.	It uses an internal controlling bus.
Microprocessor-based systems can run at a very high speed because of the technology involved.	Microcontroller based systems run up to 200MHz or more depending on the architecture.
It’s used for general purpose applications that allow you to handle loads of data.	It’s used for application-specific systems.
It’s complex and expensive, with a large number of instructions to process.	It’s simple and inexpensive with less number of instructions to process.

Features of 8051 Microcontroller:

Let's see the common feature of 8051 microcontroller:

        It having four register banks.

        64K bytes on-chip programmable memory (ROM).

        128 bytes on-chip data memory (RAM).

        Address bus is 16-bit unidirectional.

        Data bus is 8-bit bidirectional.

       128 user defined flags.

       16 bit timers.

       32 general purpose registers each of 8-bit.

      8051 microcontroller offers a number of special features such as ADC, UARTs, Op-amp, etc.

APPLICATION OF 8051 MICROCONTROLLERS :

1. Energy Management : In energy management system the measuring device is used for calculating the energy consumption in industrialized and domestic applications. These systems are manufactured by integrating the microcontrollers inside their architecture configuration.
2. Automobiles : Microcontroller 8051 is to be used for providing automobile solutions. They are largely be used in hybrid motor vehicles to control engine variations.
3. Touch screens: The advanced degree of microcontroller integrate the touch sensing ability within their design .Transportable devices such as cell phones, media players and gaming devices are some example of microcontroller integrated with touch screens.
4. Medical Devices: Microcontroller is used in various medical devices such as glucose and blood pressure measurement machine for monitoring and measuring the exact result in real-time computational environment.

8051 Microcontroller Architecture:

BLOCK DIAGRAM OF 8051:

CPU (Central Processing Unit): CPU act as a mind of any processing machine. It synchronizes and manages all processes that are carried out in microcontroller. We have no power to control the functioning of CPU. It interprets the program stored in ROM and carries out from storage and then performs it projected duty. CPU manage the different types of registers available in 8051 microcontroller.

Interrupts: 8051microcontroller have five interrupts. Interrupts is a sub-routine call that given by the microcontroller when some other program with high priority is request for acquiring the system buses the n interrupts occur in current running program.

Interrupts provide a method to postpone or delay the current process, performs a sub-routine task and then restart the standard program again.

Types of interrupt in 8051 Microcontroller:

Let's see the five sources of interrupts in 8051 Microcontroller:

              Timer 0 overflow interrupt - TF0

              Timer 1 overflow interrupt - TF1

              External hardware interrupt - INT0

              External hardware interrupt - INT1

              Serial communication interrupt - RI/TI

Memory:  In microcontroller 8051 there is code or program memory of 4 KB that is it has 4 KB ROM and it also comprise of data memory (RAM) of 128 bytes.

Bus : Bus is a group of wires which uses as a communication canal or acts as means of data transfer. The different bus configuration includes 8, 16 or more cables. Therefore, a bus can bear 8 bits, 16 bits all together.

Type of buses in 8051 microcontroller:

Address Bus: 8051 microcontrollers is consisting of 16 bit address bus. It is generally be used for transferring the data from Central Processing Unit to Memory.

Data bus: 8051 microcontroller is consisting of 8 bits data bus. It is generally be used for transferring the data from one peripherals position to other peripherals.

Oscillator:  Sequential digital circuit needs timer for their operation. To perform timer operation inside microcontroller it required externally connected or on-chip oscillator. Microcontroller is used inside an embedded system for managing the function of devices. Therefore, 8051 uses the two 16 bit counters and timers. For the operation of this timers and counters the oscillator is used inside microcontroller.

why capacitors is required with oscillator?

capacitor is required because when the crystals oscillate become old due to ageing effect its efficiency is reduce this time capacitor give a voltage trigger maintain the oscillation.