Re: Question on State Table Outputs

From: Francois Choquette (francoischoquette_at_hotmail.com)
Date: 11/10/04 

Date: 9 Nov 2004 19:28:21 -0800

There are two major state machine types : Moore and Mealy.

Moore : output is only dependent on the current state

Mealy : output is a combinatorial function of current state and
current input(s)

So, for your example, Output column should be for time (T), not (T+1).
 You may take a look at Randy H Katz Contemporary Logic Design book
from '93, available online at
http://www2.ele.ufes.br/~ailson/digital2/cld/CLD.html, chapter 8 :
Finite state machine design.

Have fun!

Francois Choquette

Steven O. <null@null.com> wrote in message news:<sgf2p0l4uvjcvh7bar9sn2mpt3uonn3tqb@4ax.com>...
> Hi. I'm taking a course on introductory digital logic, and there is a
> question where I have a disagreement with the instructor, and I think
> he may be mistaken on a certain point. We are using the text Digital
> Design by Mano, and while the book is generally very good, I think
> even the text is not fully clear on this.
>
> Suppose you have a State Table for a simple circuit with, say, two
> flip flops (A and B), input X, and output Y. So the headings for the
> table are:
>
> Present State (time T) Input (T) Next State (T+1) Output (T+1)
> A_______B__________X_______ A____ B_____________ Y
>
> Now, the question is right there in the table heading, because the
> instructor says that the output column, Y, should be for time T --
> that is, it is based on the states of A and B at time T. To me that
> makes no sense -- it seems the whole point is to start with A and B at
> time T, put in your input X, and see what A, B, and Y are at time T+1.
> So, that's basically the question -- is the output column for time T,
> or for time T+1?
>
> Thanks in advance for all replies.
>
> Steve O.
>
>
>
> "Spying On The College Of Your Choice" -- How to pick the college that is the Best Match for a high school student's needs.
> www.SpyingOnTheCollegeOfYourChoice.com

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