Introduction We are all familiar with the word “register”, yes, the same which we use in our schools days. That register is a place we write our day-to-day notes, and these notes get stored permanently in this register. So we define such register as a group of pages used to store characters. This register come in various size, the total capacity in terms of number of characters is calculated as: Capacity = (number of pages) x (number of lines) x (number of characters per line) Register: In computers also information is stored in registers. A register is a collection of storage elements that are used to store or process the binary information. The memory elements used are the flip-flops. Types of registers: a) The storage registers: The

# Sequential Circuit

Introduction In the previous posts we have focused on the design of many combinational circuits. The outputs in those circuits were dependent on the inputs applied at that instant of taking the output. Examples of such circuits were adders like half and full adders, half and full subtractors, BCD adders, Multiplexers, decoders , etc. But what if we have to add say 5, 10 or even more numbers. Practically we only two numbers at a time, store the partial result in our memory and then add this partial result(memory content) with the next numbers to get next partial sum and so on till all the numbers have been added. To save the partial results we need memory device. Such types of circuits

# Design of Counters

Introduction to Counters I remember my childhood, at a time even before going to the primary school, we used to play with pebbles, soon we started counting the pebbles. When I joined school, I realized that counting is part of our life and is used in every walk of life, count starting from zero, or starting from any number (preset). As I grew, I found counting used for different purpose; we go to refuel our vehicle, there a meter that counts the amount and the quantity of fuel; counting the marks awarded to student in an exam; days temperature, population of a city/ country, counting the score in a match, number of votes obtained by a candidate in an election, number

# Flip-Flop and Latches

Introduction The second type of digital circuitry are the sequential circuits. These circuitry are formed as a combination of combinational and the memory element. The memory element stores the state of the circuit. We start discussing on Latches and Flip-Flops. Latches Storage elements that operate with signal levels (i.e. level triggered of signal input) are termed as latches. A latch is a bi-stable element having two states Q and Q’. It is a sequential circuit that will continuously change its state as soon as the input changes without waiting for the clock signal. A latch usually has an enable input. When the enable is active the output changes as soon as there is a change in the inputs. Latches are not of practical

# Adder Circuits

Introduction In this article we will discuss the design of the arithmetic adder and subtracter circuits. These circuits will take input bits and produce two outputs sum and carry or difference and borrow. Half adder A half adder is a logic circuit that adds two bits at a time. These two bits may be the bits of two binary numbers or a bit of one number and a carry from previous stage. This circuit take two inputs and produces two outputs a Sum and a Carry. Truth table of a half adder The Sum output has two minterms and the carry output has one minterm. So the output equation in SOP form is Boolean equation are: Sum = A’B + AB’ Carry = AB The above equations do