# Multiplexer help with 74LS151 generating Y out for presupposed truth table.

#### jpegged

Joined Oct 30, 2013
2
My project incorporates two 555 timers, one monostable, one astable. Two LS74193's - decade counters. A 7404 inverter for the 8 to 1 multiplexer, a 74151. I am building on a PAD-234a trainer.
My objective is to display with LED's the hexadecimal table in binary format 0-15 from the second decade counter, after dividing by three through the first counter, from pulses generated by the oscillation of the second timer. The one shot runs for 48 seconds, the oscillator is 1 hz which provides the input for the first decade counter.

I am having a difficult time with the multiplexing. There is a table given by the instructor which the multiplexer's output should match with each digit.
ABCD Y
0000 1
0001 1
0010 0
0011 1
0100 1
0101 0
0110 1
0111 0
1000 1
1001 1
1010 1
1011 1
1100 0
1101 0
1110 1
1111 1

I am failing to understand the wiring of the 151 chip D 0-7. I have studied the datasheet quite a bit but have yet to be able to interpret the formula into a wiring scheme.

Thank you for taking a look.

#### jpegged

Joined Oct 30, 2013
2
Was able to figure out the equation. Still have a glitch on one output but after much reading and some pondering was able to solve the dilemma.

Four conditions of variable Y dependent upon the 3 input selects ABC and D or D'.

This site is a great resource. This was my first post, after two weeks of trying to solve the multiplexer problem I decided to give it a shot and post a question. Fortunately, I was able to solve the problem on my own. Regardless, thanks for maintaining this site.