Sequence Detector Using Mealy Machine

Posted : admin On 1/25/2022
Sequence Detector Using Mealy Machine

This post illustrates the circuit design of Sequence Detector for the pattern “1101”. State Machine diagram for the same Sequence Detector has been shown below. Click here to realize how we reach to the following state transition diagram.

Sequence Detector Using Mealy Machine

Click here to learn the step by step procedure of “How to synthesize a state machine / How to boil down a state machine to the circuit level”.

15-Feb-21—2:49 PM University of Florida, EEL 3701 – File 17 3 © Drs. Schwartz & Arroyo Moore & Mealy Machines EEL3701 5 University of Florida, EEL 3701 – File. Sequence Detector Mealy AIM: Design a controller that detects the overlapping sequence “0X01” in a bit stream using mealy machine. DESIGN Verilog Program- Sequence Detector 0x01 Mealy implementation `timescale 1ns / 1ps ///// // Company: TMP. 0010-and-100-Sequence-Detector Mission. To implement sequence detector which investigates input w and will produce the output z if: w is '0010' during last 4 consecutive clock cycles, or; w is '100' during last 3 consecutive clock cycles. Sequence detector should be negative-edge triggered Mealy machine with minimum number of states. Design of the 11011 Sequence Detector A sequence detector accepts as input a string of bits: either 0 or 1. Its output goes to 1 when a target sequence has been detected. There are two basic types: overlap and non-overlap. In an sequence detector that allows overlap, the final bits of one sequence can be the start of another sequence.

Now as we have the state machine with us, the next step is to encode the states. For 4 states:

StateEncoding

S0 00

S1 01

S2 10

S3 11

We need only 2 flipflops to represent these 4 states. For this example we will be using T Flipflips to design the circuit.

Sequence Detector Using Mealy Machine

Let’s draw the state transition table using the Excitation table of T flipflop

Detector
PS

Q2(t) Q1(t)

X

Input

NS

Q2(t+1) Q1(t+1)

Excite (T)

T2 T1

O

Output

0 0 0 0 0 0 0 0
0 0 1 0 1 0 1 0
0 1 0 1 0 1 1 0
0 1 1 0 1 0 0 0
1 0 0 0 0 1 0 0
1 0 1 1 1 0 1 0
1 1 0 1 0 0 1 0
1 1 1 0 1 1 0 1

Sequence Detector Using Mealy Machine For Kids

Now to realize the combinational logic we have to find out the Boolean expression for 3 output variables (of the above table) T2, T1 and O in terms of 3 input variable Q2(t), Q1(t) and X.

T2T1
YBoolean Expressions
T2 = Q2′(t)Q1(t)X’ + Q2(t)Q1′(t)X’ +

Q2(t)Q1(t)X

T1 = Q1(t)X’ + Q1′(t)X = Q1(t) ⊕ X

O = Q2(t)Q1(t)X

Let’s draw the respective circuit diagram for the given Sequence Detector.

Sequence Detector Using Mealy Machine For Beginners

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