A transceiver is bi-directional
yea well I guess thats a face palm on me
I do not believe that the HC is specified as 5V tolerant inputs. Not sure.
should be, it just cant take the current to drive older ls devices
The function of the buffer is to maintain signal integrity. Usually
buffers can drive high currents so more devices can be connected
to a data line.
See that is totally different than what I was understanding, but once I got to playing with it things were not adding up ... more on this in a moment
A buffer does two things: it effectively provides current amplification. You put a small current in its input and it can drive a larger current on its output. It also provides re-leveling. The Vih min is less than Voh min and the Vil max is more than the Vol max. The former is much more useful than the latter. Sometimes it can isolate something "bad" happening on the output from what happens on the input. Suppose the circuit on the output is noisy, and that noise would be a problem on the input side. The buffer isolates the input from the output. You often use a buffer between a "quiet" internal bus and a "noisy" external bus.
that is a pretty rock solid description
I kinda wish I didn't mention the 3v supply + 5v inputs, It didn't make since when I read it, It didn't work, and looking at how these things work I really cant see how you could even rig it, so lets scrap that (besides I already built a level shifter for that case)
now what originally got me looking at 244's and 245's was a ghetto lpt port logic analyzer, software seems ok, the hardware is basically wires coming out of the printer port BUT it was recommended by the op to use a 245 just in case, for protecting the PC if you plug it in to a higher than 5v source, and I had my doubts about that tidbit too
Would a 245 protect my pc if I accidentally touch a 15v power source? it doesnt matter after being schooled on these things I would feel better using opto's anyway
I see the practical uses of these things now, and you all have been very helpful, so thanks!