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  • Implementation of the Steering Logic

    Since for this type of counter in general we need the input to the nth T-type used to construct the circuit to be TN=Q0 *Q2*…QN-1, = TN-1* QN-1 it is clear there are two ways in which the steering logic can be generated....

    2017/11/29 zhengxiaowei 122

  • Mod-277 Synchronous Counters

    Synchronous binary counters are arguably the simplest sequential synchronous circuits. They use the flip-flops to store the circuit's count state and (usually) have no external inputs. Thus the next state (count) is determined solely by the last state (count). We again initially take an intuitive look at mod-N counters....

    2017/11/29 zhengxiaowei 128

  • 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 144

  • 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 139

  • 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 155

  • 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 161

  • 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 126

  • 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 122