TTL HEX LED driver chip

Err, no. That's what the extra inverter is for. You know hos to use a 2^n input mux to make an arbitrary combinartorial function of n signals. Feed the n signals to the select inputs of the multiplexer and wire the 'data' inputs high or low as the truth table requires. But you can also yuse a 2^(n-1) input mux and maybe a single inverte, you connect n-1 of the input lines to the select inputs of the mux. And then for each of those combinations you consider the 2 truth table lines that apply (the last input, the one you've not used yet, of course distinguishes between the 2 lines in each pair). There are 4 possibilites : a) The output of the function is 0 in both cases (it doesn't depend on the last input at all) --> wire that input of thr mux to ground b) It's 1 in both cases -> wire the input to Vcc c) It's 0, 1 , it follows the last input in this case -> Wire that last input signal to the appropraite input of the multiplexer d) It's 1,0, it's the opposite of the last input. This is when you need that inverter. Invert the last input signal and wire the appropriate multiplexer input to the ouptu of the inverter. If oyu requre several functions of the same inputs (as here), you only need 1 ivnerter (assumeing there are no fan-out problems), since it's always thge same singal (say the 2^0 data input) you need to invert. Son yes, you can use 8 input multiplexers here (and 4 input ones if you only want to generate 6 or 8 patterns). Now, another silly aside... If you want to use a 2^(n-2) mux, you may need any or all of the 16 possible functions of the last 2 inputs (you split up the truth table into sets of 4 lines, and see which function of the last 2 inputs gives the right paattern, of course). This makes it less useful :-). But it's made me think pof a chip that AFAIK never existed... If you think of those 16 possible functions of 2 inputs, then 4 of them are 'trivial' in the sense that you can produce them with no logic at all. Namely 'always 0', 'always 1', 'equal to the A input' and 'equal to the B input'. Which leaves 12 non-rtrivial ones/ Now that means there could have been a 16 pin IC with 2 power pins, 2 inputs and 12 outputs, the 12 non-trivial functions of the 2 inputs. Use that witha 74150 for an arbitrary fucntion of 6 inputs... -tony