C|B|A||Y ====== 0|0|0||1 0|0|1||0 0|1|0||0 0|1|1||1 1|0|0||0 1|0|1||0 1|1|0||1 1|1|1||1 ====== Create a set of input waveforms showing the CBA pattern and apply the proper data bits that will produce output Y Write the Boolean expression for output Y with respect to the data and select inputs. ------------------ SOMEONE HELP!
Hi Ah, engineers really like to do it the hard way. By the way, your WN output is actually the compliment of the Y output, or not-Y. We used to indicate it with a bar over the letter, but I can't put it in this text. The output Y is true when inputs 0, 3, 6 and 7 are selected. That means the other inputs are false. Just assume that the inputs are tied either high or low, and count the A, B and C selection from 0 to 7 to get the outputs.
Thanks a bunch! Could you possibly tell me how you know that 0, 3, 6, and 7 are the ones needing to be high?
Hi Electricmayhem, I know because I'm looking at my 1984 Signetics TTL data manual. The 74151 is a multiplexer. The Y output is switched an input depending on the state of the A, B and C selection bits. Look at the truth table for the states of the selection bits when Y is true. I'm assuming that A is bit 0, and C is bit 2 here. Since Y has to follow the selected input as the bits count from 0 to 7, then it follows that inputs 0, 3, 6 & 7 are high, and the others low. It may help that I've been doing this stuff for 37 years, too. I was trained as a technician, so I look at problems/designs from a different angle.