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Homework Help: Calculating the Maximum freqency of operation of a sequential machine

  1. May 27, 2009 #1
    I have to implement a sequential machine to resolve 4-bit security code . I have to use a GAL22LV10 to implement it. I've given the GAL22LV10 Circuit diagram & part of the data sheet.
    http://www.latticesemi.com/lit/docs/datasheets/pal_gal/22lv10.pdf?jsessionid=f030cc1ab4d2cec7eb8f5b38511252251a52" [Broken]

    The above link provides the complete data sheet. But in the question paper only the paged 5,7&9 are given.

    I have to calculate the maximum frequency in which the machine can operate.

    How to find the total delay in order to get the max frequency?
    I know I have to consider the propagation delay & set up time.
    Can you please send me what are the values from the data sheet I have to use to find the max delay?

    Also in which page I have to refer? (Page 7 or 9)? What's the different between them?

    Could anyone please help me to solve this problem?

    Thanks in Advance
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. May 27, 2009 #2


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    Staff: Mentor

    Welcome to the PF, Anne. You will use numbers from either page 7 or 9, depending on the speed grade of the part that you choose. The numbers for the 4ns and 5ns speed grades are on page 7, and the slower speed grades are on page 9. If you want to run as fast as possible, you will choose the 4ns speed grade parts.

    Can you post the state diagram for your state machine? How complicated is it? Do you have to do any synchronization of external asynchronous signals, or are the input bits already synchronized to the external input clock?

    Based on your state diagram and the GAL array implementation, you will use the delay numbers and setup and hold numbers to calculate how fast you can run the external clock.
    Last edited by a moderator: May 4, 2017
  4. May 27, 2009 #3
    Thank you very much Berkeman, for your quick response.

    This is my state transition table:
    (I have attached an image also)

    (y2y1y0) Next State FF Output(D2D1D0)
    X=0 X=1 X=0 X=1
    000 100 001 100 001
    001 010 101 010 101
    010 110 011 110 011
    011 000 000 000 000
    100 101 101 101 101
    101 110 110 110 110
    110 000 000 000 000
    111 xxx xxx xxx xxx

    And the simplified ff inputs are:

    o/p= x'y0y1

    Can you also please clarify me which modes to use for S1,S0 of the OLMC if I implement the array for D0 but not for D0' etc
    Is it S0S1=10 ?

    What are the facts I have to consider when marking the points in the GAL Logic diagram.
    Is the diagram which I marked & attached here is correct?

    Your help would be highly appreciated.

    Thank you.

    Attached Files:

  5. May 27, 2009 #4


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    Staff: Mentor

    I'll look at your questions in more detail later when I have time, but a couple quick thoughts:

    ** It would be helpful to show a state transition diagram, with the states labelled as to what they mean/are. You should also explicitly show that a reset vectors you to the 000 state.

    ** The 111 state should also vector to a known state, preferably the reset state. Don't ever leave states with nowhere to go, even if you never expect to get into them.
  6. May 27, 2009 #5
    Here's the original question & the steps I followed to get the answer

    Attached Files:

  7. May 27, 2009 #6
    Here're the rest

    Attached Files:

  8. May 28, 2009 #7


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    Staff: Mentor

    You didn't address the questions/points that I asked in my post #4.

    In addition, you need to post what you think the correct equations are for determining how fast you can run the clock. We do not give you the answers here. We are here to offer hints (and leading questions like I've offered) to help you answer your homework/coursework questions on your own.

    EDIT -- Actually, the timing "equations" are inequalities. Quiz Question -- why?
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