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  • Mod-N Asynchronous Counters

    A mod-W (or divide-by-N) asynchronous counter, where N=T, will count up to (N- 1) (an output of all 1’s) before resetting to all 0*s and beginning the count sequence again....

    2017/11/28 zhengxiaowei 141

  • The Introduction of Counters

    Counters are one of the most widely used logic components in digital electronic circuits. In addition to simply counting they can be used: to measure time and frequency; increment memory addresses;...

    2017/11/28 zhengxiaowei 138

  • The Introduction of Flip-flops and Flip-Flop Based Circuits

    Flip-flops' are vital ingredients in all except purely combinational logic circuits and are therefore extremely important. The SR (Set-Reset) flip-flop was introduced in the last chapter and illustrates an important point, namely that all flip, flops are asynchronous sequential logic circuits....

    2017/11/23 zhengxiaowei 152

  • Circuit 2: Movement Between States

    The previous example introduced the idea of stable and unstable total states. Using the circuit shown in Fig. 5.5 we now look at how asynchronous sequential circuits have the potential to possess memory....

    2017/11/23 zhengxiaowei 159

  • Circuit 1: Stable and Unstable States

    Consider the circuit in Fig. 5.4 which is simply an XOR gate with one of the inputs being the output which is fed back, so making it an asynchronous sequential circuit.5 (Note that in this case, Z, the external output is the same as Y, the internal output.)...

    2017/11/22 zhengxiaowei 119

  • Introduction to Asynchronous Sequential Circuits

    The essence of understanding asynchronous circuits is to realise that for the circuit to be stable the outputs generated by the input(s) must be equal (i.e. Y=y), since these two sets of signals are connected via the feedback....

    2017/11/22 zhengxiaowei 120

  • Asynchronous and Synchronous Circuits

    In this introductory text we will define two broad classes of sequential circuits, namely; asynchronous and synchronous....

    2017/11/21 zhengxiaowei 122

  • Sequential Logic Circuits: An Overview

    All of the circuits so far considered in this book have been combinational. This means that their outputs are dependent only upon the inputs at that time. We now turn our attention to sequential logic circuits whose outputs are also dependent upon past inputs, and hence outputs....

    2017/11/21 zhengxiaowei 118