BASIC KNOWLEDGE

BASIC KNOWLEDGE

MICROPROCESSOR 

It is a multipurpose , programmable logic device that reads binary instructions from a storage device called memory and accepts binary data as input and process data according to those instructions and gives output .

Classify the microprocessor into different functional blocks 

A microprocessor mainly classified into three functional blocks, namely

• Central Processing Unit(CPU)
• Memory
• Input/Output ports

What is CPU and what is its function

An 8 bit CPU is a general purpose microprocessor . It has 8 bit data length with 16 bit address bus .

The CPU fetches instructions from the memory  , decodes them into minute steps required for execution , generation of control signals accordingly and finally executes the instructions . This process continues till the whole program executes . During this process CPU is capable to take data from memory or the input ports or store them into the memory or give out data through the output ports in accordance with the program .

Classify the CPU according to different functional blocks

A CPU is basically classified into five functional blocks and they are

• Arithmetic & logic section
• General purpose register
• Control register
• Instruction register and decoder
• Timing & control unit

Describe the different functional blocks of CPU

Arithmetic & logic section

This section performs arithmetic and logic operation part of the instruction. It has three parts as Accumulator(A) , Program Status word(PSW) and ALU . The functions are completely governed by the timi8ng and control unit . In general an 8 bit microprocessor deals with 8 bit data so its operating speed is limited .To improve the speed extra circuitry . increased number of registers and pipeline is done .

General purpose register

The 8085 has 6general purpose register to store 8-bit data during a program execution. The registers are identified as B, C, D, E, H ,L

These registers are programmable meaning that a programmer can use them to load or transfer data from the register by using data . These registers are identified by specific letters for user convenience . 

Control register

There are a number of special registers which are used to perform some special functions like the selection of modes and controlling programs , memory spaces , interrupt timers , USAT. Both acc and PSW may also be known as control register . The commonly available control registers are program counter(PC) , stack pointer(SP) , index register(IX) , program status word register (PSW) .

Instruction register and Decoder

The instruction register is a control register of 8-bit in length for an 8-bit microprocessor . The instruction to be executed in first fetched into register . The decoder until decodes it into the minute steps for execution . The control unit generates necessary signals to perform these minute steps of execution . In simple µp, the decoding execution and control units are combined into one control unit. But in some powerful µp these units may be functionally independent . 

Timing &Control Unit

This unit controls all the internal and external units of a µp system . It makes the instruction to be fetched into the instruction register(IR) from the memory using PC and decodes the instruction to be executed . This operation is continued in a cyclic order so long as the power is ON . It also checks an input to the CPU that can directly alter the sequence of operation of the hardware level . This is known as INTERRUPTS .