I understand the concept of a multiplexer and I can understand how n-1 multiplexers function. Your just sending a select signal to tell the multiplexer which of the inputs at the input pins to let through on the other side.
But what does an 8-4 multiplexer work? I'm specifically talking about the 74LS257. I tried looking at the datasheets, but I still don't get it.
Best Answer
Another way of stating a 8-4 multiplexor is as four copies of a 2-1 multiplexor. The SELECT pin connects to all multiplexors, so they all choose the '0' or '1' input together. This allows you to switch 4-bit buses relatively easily with few pins.
The datasheet is a little more confusing because it includes the discrete logic version of a multiplexor. They probably did that so that the tri-state output can be shown un-ambiguously.