Designing a Circuit with Decoders and Muxes for Aisle Sale Indication

[mossfan563]

There's a store owner who has 8 aisles numbered 0-7. Each aisle has a light above it to indicate if that aisle has a sale. Only one light can be on at a time. The store owner has a switch that can be set from 0-7 and has a 3-bit output representing the switch position in binary. A second switch can be set up or down and has a single bit output that is 1 when the switch is up and 0 when down to indicate that no aisles have a sale. Design a circuit using decoders and muxes.

From what I read, I was thinking of using an 3-bit 8 to 1 mux to a 3 to 8 decoder. The only reason I'm hesitant because I'm not sure how the output of the mux goes to the decoder. Does that sound feasible? If not, what would work better?

 

[berkeman]

There's a store owner who has 8 aisles numbered 0-7. Each aisle has a light above it to indicate if that aisle has a sale. Only one light can be on at a time. The store owner has a switch that can be set from 0-7 and has a 3-bit output representing the switch position in binary. A second switch can be set up or down and has a single bit output that is 1 when the switch is up and 0 when down to indicate that no aisles have a sale. Design a circuit using decoders and muxes.

From what I read, I was thinking of using an 3-bit 8 to 1 mux to a 3 to 8 decoder. The only reason I'm hesitant because I'm not sure how the output of the mux goes to the decoder. Does that sound feasible? If not, what would work better?

For the 8 --> 3 function, can you use a priority encoder? You can use Google Images for find more info it you aren't familiar with them.

 

[mossfan563]

For the 8 --> 3 function, can you use a priority encoder? You can use Google Images for find more info it you aren't familiar with them.

No, I can't use a priority encoder. I have to start with basics. I can't use encoders. Only decoders and multiplexers.

 

[berkeman]

No, I can't use a priority encoder. I have to start with basics. I can't use encoders. Only decoders and multiplexers.

Hmm. Well, going from 8-->1 via a MUX isn't going to help you make a 3-bit input for the output demux.

[STRIKE]I'm not sure this will work, but think of a N --> 1 MUX as an OR gate. Write out a truth table for forming the 3 bit code for the 8-position switch, and see if you could use the OR function to make each of the 3 output bits from the 8 input bits...[/STRIKE]

EDITING...

Okay, I think the best hint I can give you is to make that truth table, and think about how you can use a MUX per desired output bit in the 3-bit code. Look at the table and see how many "1"s contribute to making a "1" for each bit. Does that suggest what kind of MUX(s) to use?

 

[LCKurtz]

Isn't this just a one package circuit? Run given three bits into a decoder and use the other switch for the EN input? Am I missing something?

 

[berkeman]

Isn't this just a one package circuit? Run given three bits into a decoder and use the other switch for the EN input? Am I missing something?

Oh yeah, I think you're right. I misread the OP and thought it was SP8T switch. But re-reading it, you are correct that the switch has a 3-bit output, so all he needs is the 3:8 decoder and some enable logic... Thanks for catching that.

The store owner has a switch that can be set from 0-7 and has a 3-bit output representing the switch position

 

[mossfan563]

Thank you guys! I really appreciate it!