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D-Latch [TOC]
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To build a computer, we need components (we will use so-called D flip-flops) to
store results for further calculations. To gain insight into this topic, let's
start with the so-called D-Latch. You can find this in CircuitVerse under
Sequential Elements.

---- IMAGE (width=300) -----------
session02/s02_18.png
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The functionality can be experimentally derived with the following circuit:

---- IMAGE (width=600) -----------
session02/s02_19.png
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Here's what you should observe:

- If `Enable` is set to `1`, the value of `Data in` is transferred to `Data
  stored`.
- If `Enable` is set to `0`, the value of `Data stored` remains unchanged,
  regardless of the value of `Data in`.

  ---- IMAGE (width=600) -----------
  session02/s02_20.png
  ----------------------------------

Mathematically, this can be characterized by:

---- LATEX ------------------------------------------
\text{Data}_\text{stored} =
    \text{Data}_\text{stored} \land \lnot \text{Enable}
    \lor
    \text{Data}_\text{in} \land \text{Enable}
-----------------------------------------------------

One cannot solve this implicit equation with respect to
$\text{Data}_\text{stored}$. Therefore, a D-Latch cannot be described with a
Boolean function. However, we can attempt to implement this equation using
logic gates as follows:

---- IMAGE (width=600) -----------
session02/s02_21.png
----------------------------------

Tasks
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- Implement the circuit in CircuitVerse. Confirm that the circuit behaves like
  the D-Latch.
- Change the delay of the NOT gate to 20. The circuit should no longer behave
  like a D-Latch.
- The above equation characterizes a D-Latch, but there is no instruction on
  how to implement it. For a stable implementation, the delays of the gates
  must be taken into account. We will not delve into this aspect in this
  course. However, a possible implementation should not be withheld from you:

Note
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The rule of thumb applies:

- What doesn't work in the simulator also won't work in reality.
- What works in the simulator may work in reality, but it's not guaranteed.
  Because a simulation is ultimately a model that simplifies reality.