# MSU ECE 3714 - Problem Definition (10 pages)

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## Problem Definition

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- Pages:
- 10
- School:
- Mississippi State University
- Course:
- Ece 3714 - Digital Devices at Mississippi State University

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Problem Definition Build a Finite State Machine FSM based upon your Student ID number SID FSM will have one external input called ODD If ODD is true then the FSM will reset to display the LEFTMOST odd digit in your SID and then the output will sequence over the odd digits in your SSN skipping over the even digits If ODD is false then the FSM will reset to display the LEFTMOST even digit in your SID and then the output will sequence over the even digits in your SSN skipping over the odd digits BR 2 1 99 1 Example Output Sequences For SID 458 70 2198 if ODD is true 5 7 1 9 repeat 5 7 1 9 5 7 1 9 etc if ODD is false 4 8 0 2 8 repeat 4 8 0 2 8 4 8 0 2 8 etc For SID 688 99 1234 if ODD is true 9 9 1 repeat 9 9 1 9 9 1 etc if ODD is false 6 8 8 2 4 repeat 6 8 8 2 4 6 8 8 2 4 etc BR 2 1 99 2 For ODD 0 ASM Chart For ODD 1 Dout 4 S0 S0 Dout 5 Dout 8 S1 S1 Dout 7 Dout 0 S2 S2 Dout 1 Dout 2 S3 S3 Dout 9 Dout 8 S4 We can combine these states and use ODD as a conditional input BR 2 1 99 3 1 New ASM Chart S0 0 1 odd Dout 4 Dout 5 S1 0 1 odd Dout 8 Dout 7 S2 0 1 odd Dout 0 Dout 1 To S3 next page BR 2 1 99 4 New ASM Chart cont To S0 prev page From S2 prev page S3 0 odd Dout 2 1 Dout 9 S4 Dout 8 BR 2 1 99 5 State Table Inputs Odd 0 0 0 0 0 1 1 1 1 1 Present State Next State S0 S1 S2 S3 S4 S0 S1 S2 S3 S4 S1 S2 S3 S4 S0 S1 S2 S3 S0 S0 BR 2 1 99 Outputs Dout 4 8 0 2 8 5 7 1 9 8 S4 only for even 6 2 State Encodings Have 5 states need at least three Flip Flops Binary Counting order S0 000 S1 001 S2 010 S3 011 S4 100 Grey Code S0 000 S1 001 S2 011 S3 010 S4 110 Grey Encoding oftens uses less logic than binary counting order One Hot Encoding one FF per state S0 00001 S1 00010 S2 00100 S3 01000 S4 1000 BR 2 1 99 7 What type of FFs to use D FFs are most common in Programmable logic If a PLD has a FF it will at least be able to do the DFF function We will use DFFs for this example The NextState inputs are simply the D inputs of the FFs BR 2 1 99 8 State Table Grey encoding for states Inputs

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