switches
I've come across multiple mentions of switches described as 1NO1NC.
They often described as having 2 options: ON/(OFF) and (ON)/OFF and from what I gather they have 3 terminals for wires: a NO terminal, a NC terminal and a C (?) terminal.
Can you explain what these mean?
When would you use an NO or an NC switch?
There's a few questions in there, so I'll address them one by one.
What does A x B : C Mean?
Read this as A instances of a B number of inputs to C number of outputs. What you are looking for, if I understand correctly, is a 16x2:1 or a 32x2:1 chip. If C is more than 1, then your chip is significantly more complicated - you would no longer be selecting one input and connecting it to the output. Which leads well into the next sub-question -
Why are there $200+ chips for this simple function?
The specific part you linked is a 1x32:16 wide-bandwidth, DC coupled, buffered, video MUX, which can select any of it's 32 video inputs and output them simultaneously on it's 16 buffered outputs, with a gain of 1-2x. You could sorta think of it as a 16x32:1 with a lot of features. It's got quite a bit more inside than just CMOS switches. It isn't really designed for your function, which is...
How do I connect two memories to a master CPU
The most common method for hooking up multiple memory chips to a driver/controller/cpu is to use a tri-state bus. The address lines drive both chips, and the data bus is shared between all chips. Both chips should have a pin like "output enable", which can be controlled by the CPU. I found this article discussing memory buses at a rudimentary level - it has descriptive images. See Figure 8 for the gist of what I think you want. It is the simplest way of hooking things up, and the way I would recommend if the chips support it.
How would I make one?
Well, I think you were on the right track. CPU buses can be bi-directional, so intercepting the right output enable signal may be risky. The part you were probably looking for was a digital switch, something like this 16x2:1 FET mux. This is the cheapest one at $1.75 each. Wide bidirectional buses are best handled by ICs.
Note
I would check with the maker of your CPU to look for app notes and reference designs regarding memory buses. That will be the easiest way to see if you're on track.
If the two existing buttons do not share a common GND connection then you will need a four pole double pole (4PDT) toggle switch. Such switch has twelve terminals.
If the two existing buttons share a common GND then you can get by with a double pole double throw (DPDT) switch. That switch will have six terminals.
Here is how you would connect the button flipper switch when a common GND is in place.
If the two switches do not share a common GND then you would use the 4PDT switch and basically duplicate the above circuit on the switch for the other sides of each button.
Best Answer
NO = Normally open (open = open circuit = not creating a path for the current)
NC = Normally closed (closed = short circuit = creating a path for the current)
C = Common
(The drawings show the state in the absence of force.)
When you press a normally-open pushbutton, you provide a path for the current.
When you press a normally-closed pushbutton, you impede the current from flowing.
In a relay, when the coil is not energized, C and NC are connected. When the coil is energized, the magnetic field attracts the movable metal, and C and NO are connected instead.
Uses:
a) they don't rely on creating a good contact, to signal something. They just have to open a circuit, which is much easier. An NC is more robust and therefore safer.
b) they react quicker. For an NO button, the signal event happens at the end of the movement (when the movable part makes contact). For an NC button, the signal event happens at the beginning of the movement (when the movable part stops making contact).