Forward To The Past - 4
Well Buffer Me... Having got our CPU up and running (sort of), the next step is to complete most of the core circuitry around the CPU. Historically, microprocessors were pretty fragile devices, and had a very limited fanout capability. That is, the ability to drive a number of integrated circuit inputs from it's output pins. The solution is to add a driver or "buffer" device between the CPU and anything it needs to talk to. I will concede it isn't strictly necessary in our design but since I don't know what I am going to be connecting this device to in the future, better to start with a solid foundation. Right? One, Zero and Huh? But it gets a little more complicated, and I think we need to dive into some theory. If you're an old hand feel free to skip ahead. Still here? Good... We know there are two logic states High and Low (or 1 and 0 if you prefer) and we also know that multiple devices can't share the same wire in a simple circuit bec...