Brain of Embedded System

What is Microprocessor?

The word comes from combination of micro and processor.Micro means small size and processor means a device which processes .In our context processor processes numbers 0’s and 1’s.A microprocessor, or central processing unit (CPU), is an internal hardware component that performs the mathematical calculations required for computers to run programs and execute commands. Processors are usually made of silicon material that contains tiny electrical components embedded on the surface.

“The microprocessor, also known as the Central Processing Unit (CPU), is the brain of all computers and many household and electronic devices. Multiple microprocessors, working together, are the “hearts” of datacenters, super-computers, communications products, and other digital devices.”–INTEL

Microprocessor Architecture:




Register is a small high speed named memory. It consists of a set of binary storage cells called flip-flops with parallel reading or writing or both the facilities. The number of bits in a register depends on the type and address of the data.Microprocessor picks up data from one of the registers for doing arithmetic or logical operation. Once the operation is over, it stores the result in a register. Data are usually loaded from memory to register. Similarly the resultant data will be loaded from registers to memory.

  • Accumulator is a very important register for operations in microprocessor. It is used as source of one of the operands to the Arithmetic and Logic Unit (ALU). It is also the destination of the result. The size of the accumulator is the same as the word size of the microprocessor.
  • Program counter (PC) is a register used to store the address of the instruction to be executed next in the sequence of operations. The execution of the program is initialized by loading the program counter by the address of the first instruction of the program. Once the first instruction is executed the register is automatically incremented to point to the next instruction unless a jump to a specific address is necessary. This process is repeated till the end of the program.
  • Status register (SR) is used to store the status of the microprocessor resulting from any arithmetic and logic operation. The occurrence of overflow, sign, zero, carry, etc are recorded as specific bits in this register for taking appropriate decision in the program.
  • A stack is an array of registers organized in a last in first out manner. The top of the element is always indicated by a special purpose register called stack pointer (SP). The size of the stack pointer is equal to the length of the address.


Microprocessor performs two type of operations called Arithmetic and Logic. So the basic functionality unit which consists of Arithmetic ( Addition, Subtraction, Multiplication & Division) and Logic (AND, OR, NOT) is called Arithmetic Logic Unit.

3.Timing and Control Unit

Timing and control operations are performed by timing and control unit. These operations synchronize the process of communication between µP and peripheral devices by generating the control signals necessary for communication e.g. RD and WR signals which indicate availability of data on the data bus.

Fact of the Day:

“The first microprocessor was the Intel 4004, introduced in 1971. The 4004 was not very powerful and could not perform multiplication and division– all it could do was add and subtract, it performed multiplication and division with the help of add and subtract and it could only do that 4 bits at a time. But it was amazing that everything was on one chip.”

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