It’s all Ben Eater‘s fault! Simon is more of a software and pure math champion, but Ben Eater’s videos have sparked Simon’s interest in logic and electronics, anew. Back in mid July (yes, I know, I’m a little behind with the blog), while waiting for his Complete 8-bit breadboard computer kit bundle to arrive from the US, Simon was playing with virtual circuits that he built on two wonderful platforms: Circuitverse.org and Logic.ly. You can view Simon’s page on Circuitverse at https://circuitverse.org/users/7241
Simon’s favourite was building the Master-Slave JK Flip-Flop https://circuitverse.org/simulator/edit/20037
Simon gave me a whole lecture on the differences between Sequential and Combinational Logic: in the former, there’s a presence of a feedback loop (the output actually goes back to somewhere else in the circuit), and the latter has everything going in one direction (the inputs come in and the outputs go out).
It’s a little bit like the difference between a Feed Forward neural network where the output only depends on the input and a recurrent neural network where the output also depends on what the output was previously,
Here’s a problem with sequential logic circuits: they go crazy like this very often (confused NOR gate). That’s why most sequential logic circuits have a clock in them. A clock acts like a delay so that it won’t go crazy.
That’s the power of sequential logic: you can have the same input but a different output. This is useful for storing data: I release the input, but the data is stored. It can only be archived in sequential logic.
The delay comes in error detection (on the rising edge of the square wave).
The following circuits are buit in Logicly https://logic.ly/demo