So this is a schematic for an AVR Programmer seen here: http://www.sparkfun.com/products/9825
On the bottom you will see a 74AC125 which is a Quad Buffer with Tri-State Outputs. I've seen quite a few buffers like this on programmers.....but im not exactly sure what they do? Im assuming whatever "CTL" is controls the "state" of the buffers.....but what exactly is the point? Why can't you wire it directly to whatever Port Line (Serial or w/e). Or does this have something to do with Impedance (Which Im not sure I STILL quite understand).
Is it because the Signals are coming out of the ATTINY2313 (or w/e MC is used) too fast and they need to be slowed down? I see this often when using a USB port of Serial Line....that one of these "Buffers" is used. What would happen if it wasn't there?
Or is this all just some sort of Serial Protocol Im guessing?