Tskew and timings between flip-flops

Discussion in 'Homework Help' started by Avyhe2956, Sep 14, 2016.

  1. Avyhe2956

    Thread Starter New Member

    Sep 14, 2016
    I do not understand how to approach questions of this kind.

    INTRODUCTION: I know the following formulas:

    The conditions that must exist between FF1 and FF2: (including Tskew)

    (A) T_Clk >= t_pd(FF1)+t_pd(LOGIC)+t_setup(FF2)-T_skew
    (B) t_cd(FF1)+t_cd(LOGIC) >= t_hold(FF2)+t_skew

    But, I still do not understand, for example, how to deal with the exercises below?

    For (1): what is the minimal Tclk? I prefer a full explanation than a final answer. In addition, How can I see the condition for Thold saved?

    For (2): what os the minimal Thold?

    I sit on it for a long time and can not understand.

    NOTE: I know that NOT inverts the specimen - but I can not seem to get it reflected in the formula and to understand it.


    NOTE: I never saw a formal way for this topic and I really want to understand it.

    Solution: (And i waiting for inspection / repairs / comments / answers)

    FOR (1):
    0.5*T_clk >= t_pd(FF)+t_pd(A/B)+t_setup(FF)
    --> 0.5*T_clk >= 20+10+5

    I do not completely understand how it should be. Like a or like b?
    (a). t_cd(FF)+t_cd(A/B) >= t_hold(FF) + 0.5*Tclk ?
    (b). t_cd(FF)+t_cd(A/B) >= t_hold(FF) ?

    and why?


    FOR (2):

    HOLD between FF1-->FF2:
    I do not completely understand how it should be. Like a or like b?
    (a). t_cd(FF)+t_cd(or)+t_cd(AND) >= t_hold(FF) + 0.25*Tclk + t_cd(NOT) ?
    (b). t_cd(FF)+t_cd(or)+t_cd(AND) >= t_hold(FF) + t_cd(NOT) ?

    and why?