Applied science is the basis of the inventions and latest product devel-opment. In the recent years, the
world is witnessing a revolution in the field of product development due to the application of micro-controller and Embedded Technology. (micro-
controller is a microcomputer with dedicated functions).
The dedicated microcomputers are capable to handle all complexities of Product design etc and make gadgets user friendly. For example the SIM card in a Cell phone is a micro-controller with memory. It is helpful in providing information regarding customer identification, unique mobile number and billing
amount. There are several other microcontrollers in cellular phones for transmission and receiving SMS
voice and text date, pictures etc. The above example shows that the functioning of any equipment or
machine can be improved tremen- dously by the application of microcontrollers. In most of the cases, the functional improvement is not possible without microcontrollers. Moreover, the monetary benefits derived due to enhanced quality and
functioning are much higher than the additional cost.
Microcontroller, Microcomputer,
Microprocessor
The terms are often used inter- changeably by most of us in our daily lives. But, each one is fairly
distinct from the other and it is essential to comprehend the distinct- ness at this point.
Microprocessor
A Microprocessor is Central Processing Unit (CPU) on a single chip. In the olden times companies
like Intel developed 4004 and put all the components of CPU - like the Arithmetic and Logical Unit (ALU),
decoder, registers, bus control circuit on one chip,
so the microprocessor came into picture. Although popularly known as “computer on a chip”, the
microprocessor is in no sense a complete digital computer.
The prime use of a microprocessor
is to read data, perform extensive calculations on that data, and store those calculations in a mass storage device or display the results for human use. The programs used by the microprocessors are stored in the mass storage device and loaded into
RAM as the user directs. A few microprocessor programs are stored in ROM. The ROM-based
programs are primary small fixed programs that operate peripherals and other fixed devices that are
connected to the system. Fig 1. shows the block diagram of a microprocessor CPU. Microcomputer When a microprocessor and associated support system, peripheral I/O components and memory were put together to form a small computer specifically for data acquisition and control applications, it was called a microcomputer. To make a complete microcomputer, one must add memory, usually read-only program memory (ROM) and random-access memory (RAM), memory decoders, an oscillator and a number input/output (I/O) devices, such as parallel and serial data ports. Fig 2. Shows the basic block diagram of a micro -computer.  Microcontroller An embedded microcontroller is a microcomputer that contains most of its peripherals and required memory inside a single integrated circuit along with the CPU. It is in actuality “a microcomputer on a chip”. | Like the microprocessor, a microcontroller is a general-purpose device, but one that is meant to read data, perform limited calculations on that data, and control its environment based on those calculations. The prime use of a microcontroller is to control the operation of a machine using fixed program that is stored in ROM and that does not change over the lifetime of the system. The microcontroller design uses a much more limited set of single and double byte instructions that are used to move code and data from internal memory to the ALU. Many instructions are coupled with pins on the integrated circuit package, the pins are “programmable” that is, capable of having several different functions depending on the wishes of the programmer. The microcontroller is concerned with getting data from and to its own pins; the architecture and instruction set are optimized to handle data in bit and byte size. The Intel 8051 series was one of the first microcontroller to integrate the memory, I/O, Arithmetic Logic Unit (ALU), program Rom, as well as some other peripherals, all into one very neat little package. These processors are still being designed into new products. Today there are many microcontroller families like Intel’s 8048 and 8051, Motorola’s 68 HC11, Zilog’s Z8, Microchip’s PIC, Hitachi’s H8 and now Atmel’s AVR. |  Fig 3. shows the block diagram of a microcontroller on a single chip. Comparing Microprocessors and Microcontrollers The microprocessor is designed to perform as the CPU in a microcomputer system. By configuring the microprocessor with other chips it is possible to produce a range of systems with the flexibility to provide for a range of customer requirements. The microprocessor instruction set is arranged to allow code and large amounts of data to be moved between the microprocessor and external memory using working registers and, where necessary, address pointers and offsets. Such instructions can operate on up to 32 bits of data and would usually operate on not less than 4 bits. A microcontroller on the other hand is designed to operate with the minimum of external circuitry to perform control oriented tasks using a control program in ROM. The instruction set for the microcontroller is simpler than that of the microprocessor since most of its instructions will move code and data from internal memory to the ALU. |
The operation on single bits is unique to the microcontroller since the microprocessor would generally operate on bytes or larger data groups. Fig 4. Depicts the comparison between microcontroller and microprocessor. To summarize: The fundamental differences between microprocessors and microcontrollers are as follows: • Microprocessors are intended to be general-purpose digital computers whereas microcontrollers are intended to be special purpose digital computers. • Microprocessors contain a CPU, memory addressing circuits, and interrupt handling circuits. • Microcontrollers have these features as well as timers, parallel and serial I/O, and internal RAM and ROM. • Microcontroller models vary in data size from 4 to 32 bits. Four bit units are produced in huge volumes for very simple applications, and 8 bit units are the most versatile. 16 and 32 bit units are used in high speed control and signal processing applications. • Many models feature programmable pins that allow external memory to be added with the loss of I/O capability. Microcontroller for embedded systems While discussing microprocessors we come across the term embedded systems. Microprocessors and microcontrollers are widely used in embedded system products. An embedded product uses a micro - processor (or microcontroller) to do one ta -sk and one task only. A printer is |  an example of embedded system since the processor inside it performs one task only: namely , getting data and printing it. In contrast to this a PC can be used for a number of applications such as word processor, print-server, bank teller terminal, video game player, network server, or internet terminal. A PC contains or is connected to a variety of embedded products such as keyboard, printer, mouse etc. each of which has a microcontroller inside it which performs only a specific task. For example, inside every mouse there is a microcontroller to perform the task of finding the mouse position and sending it to the PC. Microprocessor and Microcont- roller Applications Today the use of Microcontrollers and Microprocessors has shaped our lives tremendously. These versatile devices | can be found in a variety of applications, and in most of the cases their use is not visible to the user. Commercial applications such as, television sets, VCRs, CD players, microwave ovens, washing machines, telephones and smart cards are a few examples. As an example of commercial use of microcontroller, a simplified arrangement of a smart card is given in Fig 5. The microcontroller is inserted into ISO standard plastic cards with contacts that interface with external voltage supply, clock, input/output etc. The on-chip memory is divided into distinct groups namely RAM , ROM and NVM (Non- volatile memory). RAM is used to temporarily store information and is volatile i.e. it loses its contents when power is switched off.  |
Ref. foryou/feb2007