ECS154A-L10

📗 -> 01/29/25: ECS154A-L10

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[Lecture Slide Link]

🎤 Vocab

❗ Unit and Larger Context

Small summary

✒️ -> Scratch Notes

Design electronic lock which opens when user enters 3 values in correct sequence

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2 buttons

L+R
Opens when LRL

States:
Inputs:
Outputs:

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• Moore model

Moore Model

Output function only of the state

Mealy Model

Output is a function of the state and input

• The above lock scenario is a Moore model

Pros and Cons:

• Mealy models use less states
  • They are cheaper
• Moore models are more stable
  • Computers want stability, are Moore models

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• Mealy model

5 Steps to Designing an SSC

SSC - Synchronous Sequential Circuit

1. Model provided specs (make state transition diagram)
2. Minimize the number of states in the model
3. Create State Transition Table
4. Select flip-flops and write flip-flop equations
5. Design the combo logic

Assume machine M1:

• Single input, single output SSC which determines if previous 4 inputs constitute valid BCD (binary coded decimal) codeword

Refresher: BCD = Binary Coded Decimal = 0000-1001

z to indicate valid, z=1 invalid
least significant bit appears 1st in time, each clock new x presented oldest X discarded

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• Continues on for all 16 inputs

Current State	Next x=0	State x=1	Output x=0	Output x=1
000	000	100	0	0
001	000	100	0	0
010	001	101	0	1
011	001	101	0	1
100	010	110	0	1
101	010	110	0	1
110	011	111	0	1
111	011	111	0	1

• Group inputs, as we see there are identical inputs/outputs
  • A: 000, 001
  • B: 010, 011
  • C: 100, 101
  • D: 110, 111
    

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Current State	Next x=0	State x=1	Output x=0	Output x=1
A	A	C	0	0
B	A	B	0	1
C	B	D	0	1
D	B	D	0	1

• Theoretically could combine C and D, but need 2 flip flops for 3 inputs or 4 so no real benefit
• Need to assign states to names
  • A:
  • B:
  • C:
  • D:
• This representation will be the language our circuit works in

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