Setup time electronics

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How do we use it in out application? Thanks in advance. The time [after the active clock edge] for which the DFF output maintains its value before switching is characterized as the hold time for that DFF. Following is the list of recommended gadgets for your electronic lab. If you have plenty of money, you can buy a pre-built electronic workbench. I found a couple of good ones on sale on Amazon. Some of these come with plug points and storage cabinets. These are probably overkill for hobby electronics.

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Similar to setup time, each sequential element needs some time for data to remain stable after clock edge arrives to reliably capture data. This duration is known as hold time. The data that was launched at the current edge should not travel to the capturing flop before hold time has passed after the clock edge.

Adherence to hold time ensures that the data launched at current clock edge does not get captured at the same edge. In other words, hold time adherence ensures that system does not deviate from the current state and go into an invalid state. As shown in the figure 1 below, the data at the input of flip-flop can change anywhere except within the seup time hold time window. A D-type latch. A complete D flip-flop using the above structure of D-type latch is shown in figure below:.

Now, let us get into the details of above figure. If that is not the case, it will be accounted for accordingly. Shown above is a flop-to-flop timing path. For simplicity, we have assumed that both the flops are rise edge triggered. The setup and hold timing relations for the data at input of second flop can be explained using the waveforms below:.

Figure showing setup and hold checks being applied for the timing path shown above. As shown, data launched from launching flop is allowed to arrive at the input of the second flop only after a delay greater than its hold requirement so that it is properly captured.

Similarly, it must not have a delay greater than clock period — setup requirement of second flop. In other words, mathematically speaking, setup check equation is given as below assuming zero skew between launch and capture clocks :. Similarly, hold check equation is given as:. If we take into account skews between the two clocks, the above equations are modified accordingly. If T skew is the skew between launch and capture flops, equal to latency of clock at capture flop minus latency of clock at launch flop so that skew is positive if capture flop has larger latency and vice-versa , above equations are modified as below:.

If the setup check is violated, the data will not be captured at the next clock edge properly. Similarly, if hold check is violated, data intended to be captured at the next edge will get captured at the same edge.

It may lead to metastability failure in the design as explained in our post ' metastability '. On the other hand, a design with hold violation cannot be run properly.