Sequential Circuit Design Moore Design Output is a function of - PowerPoint PPT Presentation

Sequential Circuit Design

Moore Design Output is a function of present state only

Mealy Design Output is a function of present state and input

Example The vending machine delivers a pack of gum after it has received 15 cents in coins. It has a single coin slot that accepts nickels or dimes, one at a time. A mechanical sensor indicates to the FSM whether a nickel or dime has been deposited and it will be asserted every clock period. Implement the system using both Mealy and Moore designs. Few Assumptions: 1. If the customer has deposited two dimes, a single pack of gum will be released and the remaining nickel is not returned. 2. It is not possible to deposit nickel and dime at the same time

Five Steps 1. Draw State Diagram [Mealy or Moore as required] 2. Do State Assignment 3. Draw State Transition Table 4. Derive Boolean Expressions 5. Draw circuit

STEP 1 : Moore State Diagram

STEP 2 : State Assignment S0 00 S1 01 S2 10 S3 11

STEP 3: STATE TABLE Current State Input Next State Output Q1(t), Q0(t) D, N Q1(t+1), Q0(t+1) Y 00 00 00 0 00 01 01 0 00 10 10 0 00 11 XX 0 11 00 11 1 11 01 11 1 11 10 11 1 11 11 XX 1 Similarly complete the remaining table

STEP 4, 5: Boolean Expressions, Circuit Using the State table, write the equations in the form Q0(t+1) = f (Q0(t), Q1(t), N, D) Q1(t+1) = g (Q0(t), Q1(t), N, D) Y = h (Q0(t), Q1(t)) We can follow the same procedure for Mealy Design with few changes

STEP 1,2 : Mealy State Diagram, State Assig. S0 00 S1 01 S2 10 S3 11

STEP 3: STATE TABLE Current State Input Next State Output Q1(t), Q0(t) D, N Q1(t+1), Q0(t+1) Y 00 00 00 0 00 01 01 0 00 10 10 0 00 11 XX X 11 00 11 1 11 01 11 1 11 10 11 1 11 11 XX X Similarly complete the remaining table

STEP 4, 5: Boolean Expressions, Circuit Using the State table, write the equations in the form Q0(t+1) = f (Q0(t), Q1(t), N, D) Q1(t+1) = g (Q0(t), Q1(t), N, D) Y = h (Q0(t), Q1(t), N, D)

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