Microsoft Word - Digital Logic Design v_4_6a

• Draw the Present/Next State Table


• Write the Excitation-Input Equations
  Di = Σ(PS.external input for set) + Σ(PS.external input for hold 1 )


• Draw the schematics

 Set-Clear Method for obtaining T Excitation-Input Equations

The following table will be used to write T excitation equations directly from a state diagram, ASM

chart, or a timing diagram.

Present State
(PS/NS)
Yi Yi+

Ti

Comment

User for 1s

(Set-Hold 1)

Use for 0s

(Clear-Hold 0)

0 0

0 1

1 0

1 1

0

1

1

0

Hold 0 transition

Set transition

Clear transition

Hold 1 transition

Ti

Ti

Ti’

Ti’

 The “Set – Clear Method” can be used to obtain the T excitation equations for the 1s of each

state variable (flip flop outputs)

Ti = ∑ (PS .external input conditions for set) + ∑ (PS .external input conditions for clear)

for i = 1,2,3,...

Note: This method solves for the 1’s of the function.

 We could also apply the “Hold 0 - Hold 1 Method” to obtain the T excitation equations for the

0s of each state variable (flip flop outputs)