ECE 275: Digital Design I

Class 26

Mealy State Machine Example

Detect 10101 with overlaps

S0: RESET, 0 S1: 1 S2: 10 S3: 101 S4: 1010

10 -> S2 11 -> S1

100 -> S0 101 -> S3

1010 -> S4 1011 -> S1

10100 -> S0 10101 -> S3

CS X=0 X=1 X=0 X=1
S0 S0 S1 0 0
S1 S2 S1 0 0
S2 S0 S3 0 0
S3 S4 S1 0 0
S4 S0 S3 0 1

^ State Table

CS X=0 X=1 X=0 X=1
000 000 001 0 0
001 010 001 0 0
010 000 011 0 0
011 100 001 0 0
100 000 011 0 1

^ State Assigned Table

Da = Db = Z = X Qc Qb' * Qa'

XQc\QbQa 00 01 11 10
00 1
01
11 1
10 1

Db = X'Qc'Qb'Qa + XQcQb'Qa' + XQc'QbQa'

Armstrong Humphrey Rules

(for minimal state assignment rules) - ECE 375

ECE 375 - Will be asked to do a Mealy or Moore that matches X sequence