States Tables, Latch and Flip Flop The D Flip Flop student version

States Tables, Latch and Flip Flop The D Flip Flop student version

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1 EC262 Topic 11: The D Flip Flop Clocks We saw when looking at the R-S latch that an instability can arise if we allow R = 1 and S =1, and then drive R and S to 0 at the same time. This instability is avoided by not permitting the state R =1 and S =1 to occur in the first place. This type of instability problem can occur in other ways. If a number of R-S latches are interconnected together, it is important that the various elements switch their states at the same time, in a coordinated and controlled fashion. This can be accomplished by distributing a periodic enable signal throughout the system, with each memory device only permitted to switch states when enabled. This single enable signal, which periodically activates, thereby enabling all of the devices at the same instant, ensuring that all state shifts are synchronized, is called A system of sequential elements that all change their states at the same time is termed a In a synchronous system, all sequential elements can change state only once per periodic clock signal, and no elements can alter their states between clock signals. Clock signals, such as those shown below, are characterized by two values. From A. Marcovitz, Introduction to Logic Design , McGraw Hill, 2010 The _______________ , which is the The (i.e., 1 for active high, 0 for active low). The signals above have the Do you think that we want clocks to have a high frequency or a low frequency (or it doesn’t matter)? Most good computers have a clock rate of around Do you think that we want clocks to have a high duty cycle or a low duty cycle (or it doesn’t matter)?
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2 The R-S Latch Under the Control of a Clock Explain the operation of the circuit below: From A. Marcovitz, Introduction to Logic Design , McGraw Hill, 2010 We must worry about the stability of S and R only during the time that Suppose we have that terrible situation of setting S and R both to 1, and then simultaneously shifting them to 0. What happens?
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This note was uploaded on 03/27/2012 for the course ECE 200 taught by Professor Nasis during the Spring '08 term at Drexel.

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States Tables, Latch and Flip Flop The D Flip Flop student version

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