A review on

Stroke is a common worldwide health problem and a crucial contributor to gained disability. The abilities of people, who are subjected to stroke, to live independently are significantly affected since affected upper limbs ’ functions are essential for our daily life. This review article focuses on emerging trends in BCI-controlled rehabilitation techniques based on EMG, EEG, or EGM + EEG signals in the last few years. Working on developing rehabilitation robotics, is considered a wealthy scientific area for researchers in the last period. There is a significant advantage that the human acquires from the interaction between the machine and his body, rehabilitation for a patient ’ s limb is very important to get the body limb recovery, and this is what is provided mostly by applying robotic devices.


INTRODUCTION
Computer: It is electronics programmable logic system. Which consists of CPU memory and I/O interfaces in which with the help of memory and I/O interfaces CPU executes the program to perform basic various arithmetic and logical operation and digital data world to meet specific task. Microprocessor: An integrated circuit that contain all the function of CPU of computer. The microprocessors have always been designed for their performance and cost keeping in mind. Gordon Moore who was the founder of Intel Corporation predicted that the number of transistors on a chip will almost be double once in every two year to meet this ever growing demand which is popularly known as Moore's Law in the semiconductor industry. In present days the integrated circuit processing technology increasing integration density which has made it possible to integrate one billion transistors on a single chip for the improved performance. The microprocessors which evolved from the invention of transistors and integrated circuits are today an icon of the today change. From fastest computers to the simplest toys, the microprocessor continues to find new application. Everyone who works in the computer industry is well familiar with Moore's Law and the doubling of the number of transistors (an approximate measure of computer processing power) every 18 to 24 months. Until recently, overall microprocessor performance was often described in terms of processor clockspeeds, expressed in megahertz (MHz) or gigahertz (GHz).Today there's far more than clock speed to consider when you're evaluating how a given processor will perform for a given application and where it fits on the performance scale. Microprocessor designers today are more focused on methods that leverage the latest silicon production processes and designs that minimize microprocessor footprint size, power consumption and heat generation. In advanced fabrication chip techniques there is big problem of bottleneck, power dissipation issues. From studied on it we can say that the transistor leakage current increases as the chip size reduced further and it will increases the static power dissipation to large values as shown in figure1 below. There is one change means to improve the performance and is to increase the frequency of operation which makes it fast execution of programs. As we increases the frequency beyond this limit it will increases power dissipation again. The microprocessor has always pushed the technology of the today. The desire of ever increasing performance has led to the rapid improvement of the technology that have enabled more complex microprocessors. Advances in IC fabrication processes, computer architecture, and design methodology, have all been required to create the microprocessor of today. Some microprocessor designs of the past have been overly complex and have relied on out-of-order logic to reshuffle and optimize software instructions. Going forward, microprocessor designers will continue to deliver better and better software tools, higher software optimization and better compilers. Because it is so efficient and so small and doesn't depend on out-of-order logic. The most successful microprocessor implementations depend not simply on the use of the current state of the art in hardware algorithms, but more importantly in bringing together the knowledge of these algorithms together with projected advances in the technology and user state of the art.

II. THE HISTORY OF MICROPROCESSOR
The history of the microprocessor begins with the birth of the Intel 4004 the first commercially available microprocessor. It evolved from the inventions of the transistors and integrated circuits. In 1968, Intel Corporation was founded to exploit the semiconductor memory market, which uniquely fulfilled these criteria. Early semiconductor RAMs, ROMs, and shift registers were welcomed wherever small memories were needed, especially in calculators and CRT terminals, In 1969, Intel engineers began to study ways of integrating and partitioning the control logic functions of these systems into LSI chips.
Intel embarked on the design of two customersponsored microprocessors, the 4004 for a calculator and the 8008 for a CRT terminal. The 4004, in particular, replaced what would otherwise have been six customized chips, usable by only one customer, Because the first microcomputer applications were known, tangible, and easy to understand, instruction sets and architectures were defined in a matter of weeks. Since they were programmable computers, their uses could be extended indefinitely. Both of these first microprocessors were complete CPUs-on-a-chip and had similar characteristics. But because the 4004 was designed for serial BCD arithmetic while the 8008 was made for 8-bit character handling, their instruction sets were quite different. The succeeding years saw the evolutionary process that eventually led to the 8086. Table 1 summarizes the progression of features that took place during these years.

III. CONTROL UNIT
Control unit is a very important unit as it synchronizes the registers and flow of data through various registers and other units. This unit consists of an oscillator and controller sequencer which sends control signals needed for internal and external control of data and other units.

IV. ARITHMETIC AND LOGIC UNIT
There is always a need to perform arithmetic operations like +, -, *, / and to perform logical operations like AND, OR, NOT etc. So there is a necessity for creating a separate unit which can perform such types of operations. These operations are performed by the Arithmetic and Logic Unit (ALU). But these operations cannot be performed unless we have an input (or) data on which the desired operation is to be performed. So from where do these inputs reach the ALU? For this purpose accumulator is used. ALU gets its Input from accumulator and temporary register. After processing the necessary operations, the result is stored back in accumulator.

V. ACCUMULATOR
The accumulator is also called an 8-bit register. The accumulator is connected to Internal Data bus and ALU (arithmetic and logic unit). The accumulator can be used to send or receive data from the Internal Data bus. The data to be processed by arithmetic and logic unit is stored in accumulator.

VI. REGISTERS
The 8085/8080A-programming model includes six registers, one accumulator, and one flag register, as shown in Figure. In addition, it has two 16-bit registers: the stack pointer and the program counter. They are described briefly as follows. The 8085/8080A has six general-purpose registers to store 8-bit data; these are identified as B,C,D,E,H, and L as shown in the figure. They can be combined as register pairs -BC, DE, and HL -to perform some 16-bit operations. The programmer can use these registers to store or copy data into the registers by using data copy instructions.

VII. FLAGS
Flags are nothing but a group of individual flip flops. The flags are mainly associated with arithmetic and logic operations. The flags will show either a logical (0 or 1) (i.e.) a set or reset depending on the data conditions in accumulator or various other registers. A flag is actually a latch which can hold some bits of information. It alerts the processor that some event has taken place. Intel processors have a set of 5 flags. Used segment registers to access more than 64 KB of data at once, which many programmers complained made their work excessively difficult.