NOTE BOOK - Computer Architecture and System Software

 NOTE BOOK - Computer Architecture and System Software

Date: 18/01/2021

ENCODER :- encoder is a combinational circuit which is designed to perform the inverse of the decoder. An encoder has n number of input lines and m number of output lines. An encoder produces an n bit binary code accepts an n input digital word and coverts it into an m bit another digital word.

Block diagram of Encoder -

Types of encoder -

• 1.      Priority encoder
• 2.      Octal to binary encoder
• 3.      Hexadecimal to binary encoder

Priority encoder -

This is a special type of encoder. Priority is given to the input lines. If two  or more input lines are at the some time, the input with the highest priority will be considered.

Ther are 4 inputs D0 D1 D2 D4 out of four D3 has highest priority and D0 has the lowest priority

That means if D3=1 then Y1Y1= 11 irrespective of the other inputs, similarly if D3=0 and D2=1 then Y1Y0=  ____________________________

Logic circuit

Flip Flop:-   Flip flop is a sequential circuit which generally samples its inputs and charges its output only at particular instants of time and not continuously. Flip flop is said to be edge sensitive or edge triggered rather than being triggered like latches. (flip flop = latches (ek tarah se )  storage elements operates on signal level. Controlled by clock transition sequential me latches ko add kiya gaya hai  storage elements ke tor pe.) 

S-R Flip Flop :-   ( Set Reset flip flop )

D flip flop is a slight modification of SR Flip Flop

 From the above figure you can see that the D input is connected to the S input and the Complement of F input is connect to the R input When the above cp is 1 (high) the flip flop moves the set state if it is 0 (low) the flip flip switches to tje clear state

T- Flip Flop - ( simpler version of JK ) = This flip flop is a much simpler version of the JK flip flop 

Triggering of flip flops

    the state of the flip flop is changed by a monetary change is known as trigger and the transition it causes is said to triggering the flip flop

A pulse start from the initial value of O goes momentarily to 1 and after a short while returns to its initial 0 value is either positive or negative. 

A positive clock remains at 0 during the interval between pulses and goes to 1 during the occurrence of a pulse.  

The pulse goes through two signal transition: from '0' to '1' and return from '1' to '0'.

The positive transition is defined as a positive edge and the negative transition as a negative edge.

register is a fast memory to store accept and transfer data and instructions that are immediately use by cpu 

- a register can also be considered as a group of flip flop wit each flip flop capable of storing one bit information

- a register with n flip flops is capable of storing binary information of n bits

Shift Registers

shift registers are capable of shifting their binary information in one or both directions, the logical configuration of a shift registers consist of a series of flip flop with the output of one flip flop. connected to the input of the next flip flop.

the control of the flow of shift, ie the flow of binary information from one register to the next, a common clock is connected i series, this clock generates in clock pulse which initiates the shift from one stage to the next.

- the most general shift registers are often referred to as bidirectional shift registers with parallel load

- a common clock is connected to each registers in series to synchronize all operations 

- a series intone line is associated with the left ,most register and a series output line is associated with the right most register. 

- a control state is connected which leaves the information in the register unchanged even though clock pulse are applied continuously.