Combinational & Sequential Circuits Multiplexer S-R Flip-flop JK-flip-flop

digital electronics

555 Timer

555 Timer:

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package.

The 555 Integrated Circuit (IC) is an easy to use timer that has many applications. It is widely used in electronic circuits and this popularity means it is also very cheap to purchase, typically costing around 30p. A 'dual' version called the 556 is also available which includes two independent 555 ICs in one package. 

Combinational and Sequential Logic Circuits - Digital Circuits

Digital circuits can be classified into two types:

Download :Combinational and Sequential Logic Circuits

→ Combinational digital circuits and

→ Sequential digital circuits.

Combinational Digital Circuits:

• In these circuits “the outputs at any instant of time depends on the inputs present at that instant only.” are made up from basic gates (AND, OR, NOT) or universal gates (NAND, NOR) gates that are "combined" or connected together to produce more complicated switching circuits. These logic gates are the building blocks of combinational logic circuits. An example of a combinational circuit is a decoder, which converts the binary code data present at its input into a number of different output lines, one at a time producing an equivalent decimal code at its output.

Counters - Ripple(Asynchronous) Counters and Synchronous Counters

Counters:

Download: Counters Notes

• Counters are sequential circuits that cycle through some states.

• They can be implemented using flip-flops.

• Implementation is simple: using T flipflops (with toggle output) or with any other flip-flops that can be connected to give the required function.

Counters are 2 types:

1. Ripple(Asynchronous) Counters.
2. Synchronous Counters.

Latches and Flip-Flops Notes - Digital Circuits

Latches and Flip-Flops:

Download:  Latches and Flip-Flops Notes

• Latches and flip-flops are the basic elements for storing information.
• One latch or flip-flop can store one bit of information. The main difference between latches and flip-flops is that for latches, their outputs are constantly affected by their inputs as long as the enable signal is asserted.
• In other words, when they are enabled, their content changes immediately when their inputs change. Flip flops, on the other hand, have their content change only either at the rising or falling edge of the enable signal.
• This enable signal is usually the controlling clock signal. After the rising or falling edge of the clock, the flip-flop content remains constant even if the input changes.
• There are basically four main types of latches and flip-flops: SR, D, JK, and T. The major differences in these flip-flop types are the number of inputs they have and how they change state. For each type, there are also different variations that enhance their operations. In this chapter, we will look at the operations of the various latches and flipflops.

Latches:

 A temporary storage device that has two stable states (bistable)

 The S-R (Set-Reset) Latch (also called a multivibrator)

 it is based on enable function input

 it is a level trigerred , it mean that the output of present state and input of the next state depends on the level that is binary input 1 or 0.

Digital IC Families

Digital IC Families:

View:

Digital Electronics- Boolean Algebra (Part 1)

Boolean Algebra:

Boolean algebra derives its name from the mathematician George Boole. Symbolic Logic uses values, variables and operations :

• True is represented by the value 1.
• False is represented by the value 0.

Variables are represented by letters and can have one of two values, either 0 or 1. Operations are functions of one or more variables.