Question triggering edge


Jul 27, 2020
Propagation delay is the time duration taken for a signal to reach its destination. It can relate to networking, electronics or physics. Hold time is the minimum interval required for the logic level to remain on the input after triggering edge of the clock pulse.
What is triggering edge? What are the methods increase it (if it possible)? Does it possible?
From Wikipedia - Signal propagation delay value?


This is pretty well laid out in the Wikipedia page and the linked pages, not sure I can explain it better.

If you imagine a square wave of any digital signal. The triggering edge is when the signal transitions from the ground/low (zero) state to the high (one) state. While a true square wave is instantaneous, a real one will have a discrete measure of time before the high state is reached (sometimes with some overshoot). Those the angled ramp up and down in the wikipedia images. Hold time is the time it must stay in that state to register as a high (one). Too short a pulse and it may not be interpreted as the desired state.

Essentially, when designing a circuit or logic, propagation delay must be taken into consideration. If it takes too long for a signal to get through, then the hold up time requirements of the next circuit may be missed and you will have a data/logic error.

As to increasing or decreasing delay, that depends on too many factors. I would say generally difficult to decrease delay without a significant hardware change, such as a faster medium, or reduction of logic steps. Increasing is easy, you can add more logic, or build in accumulation time in the form of capacitors, resistors, coils, length of board traces. Enforce timings with external clock frequencies.

Here is a brief on HDMI signals which is relevant:

Eye diagrams are a way to see if a signal is within the acceptable range of a particular standard. Anything inside the "Eye" would be bad.