Inputs and Outputs 2: input limitations

It seems obvious that an output can push its charge to any number of inputs. What's less obvious is whether multiple outputs can feed into a single input.

Expanding on our trusty light bulb setup from last time: instead of having 1 power source + switch before the bulb, lets have 2 sets like this in parallel. Now if either switch (or both) are closed then the bulb lights up.







Stand in awe of my mighty illustration skills!

There are a few ways to handle this:

1. The bulb's input can accept from multiple output sources
2. The output sources combine into 1. If either or both sources are charged, the bulb lights up. This is an "OR" relationship. Expanding on that:
3. The sources must enter an OR gate and the single output from that gate will be the bulb's input

These solutions go from most simple to most complex, so why don't we choose the 1st and simplest? Actually, there is a reason and it's largely academic. What we're doing in sHs is an exercise in "sequential logic." That is: using boolean (on/off) values, we're moving in a linear sequence, evaluating as we go. This is a very old idea and there are certain conventions that are used. #3 above follows said convention.

Make no mistake, we are in no way bound by these conventions. There are no teachers standing over our shoulder ready to whack our knuckles for doing our program in an unorthodox or colloquial way. Back in Transistor choice when we were trying to choose whether to use MOSFET+CMOS logic, I had no problem justifying a simpler way of doing things. However, in this case, I'm still going to opt for #3 anyway because it makes sense in my mind.

Regardless of which option you prefer though, we should all agree on one important point: the multiple inputs must resolve to a single collective ON or OFF value before we can determine whether the bulb should light. Any of the 3 above can achieve this.