how to draw state diagram of sequential circuit?

How to draw state diagram of sequential circuit?

how to draw state diagram of sequential circuit? It is actually the graphical representation of logic circuits. The state diagram is a visual representation of how sequential circuits behave. It clearly depicts the transition of states from one state to the next, as well as the output for a given input. Each current state is represented by a circle in this graphic.

Flip-flops can be graphically represented by a state diagram in addition to graphical symbols, tables, or equations. A state is represented by a circle in this picture, with directed lines (or arcs) connecting the circles indicating the transition between states. Different forms of state diagrams exist, each with its own meanings and characteristics. State diagrams depict finite state machines graphically. They’re solely utilized to figure out how objects behave across the entire system. An example of a state diagram is show below

state diagram
state diagram

Each circle has a binary number inside it that represents the condition it represents. Two binary numbers separated by a slash (/) are used to label the directed lines. The input value that triggers the state shift is the first to be labelled. The value of the output is the number after the slash symbol /. The directed line from state 00 to 01, for example, is labelled 1/0, which means that if the sequential circuit is in a current state with a 1 as an input, the following state is 01 with a 0 as an output. If the input is 0 and the current state is 00, it will remain in that state. A circle connected to itself by a directed line shows that no change of condition has occurred.

Although state diagrams are an important and valuable modelling approach, they are not required for every class. The interaction between objects of different classes causes complexity in most systems, as shown in sequence and collaboration diagrams. It’s possible that only a few classes in any system, particularly an information system, will exhibit dynamic behavior, necessitating the use of a state diagram to depict what happens. This is the situation in a system like Wheels, where most classes have objects that only go through a limited number of events and all of the objects react the same way to the same event. In the Wheels case study system, for example, all Customer objects respond to events in the same way, but with varying values: recording details, locating a corresponding Hire object, displaying customer details, and editing customer details. Their reaction to events is independent of their current state. There isn’t much to display on a state diagram for this type of class, which has pretty straightforward behavior. Other types of computer systems, such as process control or communication systems, may feature a lot of classes with exceedingly complex dynamic behavior.

A state diagram is made up of rounded boxes that represent states and arrows that depict transitions to the next state. The actions that the object engages in while in that condition are depicted in the activity section. Every state diagram begins with the initial state, which is where the item is created. Objects change states immediately after the initial state, and the next state is selected by activity-based circumstances. State diagrams can sometimes illustrate a super state, which is a phenomenon that occurs when multiple transitions lead to a single state.

What is the Gray Code? 

The Gray Code, also known as reflected binary code, is a series of binary number systems. The initial N/2 values are compared to the last N/2 values in reverse order, which is why this code is called reflected binary code. Two successive values are separated by one bit of binary digits in this coding. In the general sequence of hardware-generated binary numerals, grey codes are employed. When transitioning from one number to the next, certain numbers might generate ambiguity or problems. When the transition between numbers is complete, this code simply addresses the problem by modifying only one bit.  Gray code assesses the nature of binary code, or data made up of on and off signs, which are frequently represented by ones and zeros. Gray code, developed by Bell Labs scientists, has been used to investigate binary communications clarity and error correction. Gray code, also known as reflected binary code, is a type of binary coding.

Gray code essentially sophisticates and clarifies binary outcomes. Physical switches for binary code are discussed as part of this procedure; nevertheless, experts warn that physical switches may not synchronize perfectly. Other issues include signal noise, which can result in transmission issues due to lost binary bits or integers.


Gray code does this by looking at one switch or piece of binary code at a time, and going through binary code slowly looking for consistency. Applications for digital terrestrial TV transmissions and cable-delivered digital signals are two common examples. Because it is not dependent on the value of the digit indicated by the location, the grey code is a very light weighted code. This code is also known as a cyclic variable code since the transition from one value to the next only changes one bit. Because it is not dependent on the value of the digit indicated by the location, the grey code is a very light weighted code. This code is also known as a cyclic variable code since the transition from one value to the next only changes one bit.

To generate the Gray code of a number, the prefix and reflect methods are applied recursively. To generate grey code, follow these steps:


  • The amount of bits required to represent a number is determined.
  • Then we look for the code for zero, which is 0000, which is the same as binary.
  • Now we’ll replace the most significant portion of the prior code, which is 0000.
  • We carry doing this procedure in secret until all of the codes are unidentifiable.
  • If changing the most significant bit yields the same result as changing the second most significant bit, the third most significant bit will be altered, and so on.

Gray code is a type of non-weighted code that is a subset of unit-distance code. The bit pattern for two consecutive numbers differs in only one-bit location in unit-distance code.

For example, these codes are sometimes known as cyclic codes.

  • The decimal number 5 is represented by the grey symbol 0 1 1 1
  • 0 1 0 1 is the grey cod for the decimal number 6.

The only difference between these two codes is one-bit location.

Because of this feature, this code is widely employed in shaft encoders.

  • Gray code is code that has been reflected.
  • The following property can be used to create grey code.

i)1 Bit Gray Code has two code words, 0 and 1, which represent decimal numbers 0 and 1.

  1. ii) An n>2 (n-bit) Gary Code will have the leading 0 appended to the first 2n-1 Gray Codes of (n-1) bit written.

iii) The final 2n-1 Gray Code will be the reverse order Gray Code words of a (n-1) bit Gray Code.

The table below will help you to understand the concept better .

Gray code Table
Gray code Table

The comparable grey coding of decimal numbers can be found in this table. There are various procedures that will help you comprehend how codes are constructed. In the case of grey code, each step will modify one bit from the preceding one. One thing to remember is that bit changes always happen on the right side, from the L.S.B to the M.S.B. The first three bits remain constant, i.e. 000, but the fourth bit shifts from 0 to 1. We know that the only binary digit combinations are 0 and 1, therefore keeping the first three bits constant eliminates the possibility of a 4th bit combination for decimal 0 and 1.

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