Hello I'm in a first year digital logic class and have just had a test. There was a bonus question that I got partial marks for but am really wondering how I could have gotten full marks. We don't get the tests back to see what was right or wrong, just the mark. I will show what was asked and what i did. It has to do with designing a circuit with the fewest number of logic gates to complete.
The question went something along the lines of "using three toggle switches (A, B, C) design a circuit using only logic gates (and or nand nor xor xnor not) or latches or flip flops (SR, D, JK) that turn on 3 lights. If zero or one switch is on turn on light 1. If 2 switches are on turn on light 2. If all three switches are on turn on lights 1,2 and 3. Do this using the fewest number of gates possible. Inverters (nots) do not count towards your total, use as many as you want. You can not split the outputs from any logic gate
I started by creating a truth table
A B C Lt1 Lt2 Lt3
0 0 0 1 0 0
0 0 1 1 0 0
0 1 0 1 0 0
0 1 1 0 1 0
1 0 0 1 0 0
1 0 1 0 1 0
1 1 0 0 1 0
1 1 1 1 1 1
I created 3 karnaugh maps and came up with the following boolean expressions
A'B'+A'C'+B'C'+ABC = Lt1
AB+AC+BC= Lt2
ABC = Lt3
(I hope I'm remembering this correctly)
Putting this all together I came up with 10 gates as written above (8 and gates and 2 or gates, using 3 inverters)
I'm not very good with flip flops or latches etc. Could there be a way of reducing the above further using these? I received half marks for this bonus question.
Help! I'm stumped! I've spent all weekend dwelling on this!!
The question went something along the lines of "using three toggle switches (A, B, C) design a circuit using only logic gates (and or nand nor xor xnor not) or latches or flip flops (SR, D, JK) that turn on 3 lights. If zero or one switch is on turn on light 1. If 2 switches are on turn on light 2. If all three switches are on turn on lights 1,2 and 3. Do this using the fewest number of gates possible. Inverters (nots) do not count towards your total, use as many as you want. You can not split the outputs from any logic gate
I started by creating a truth table
A B C Lt1 Lt2 Lt3
0 0 0 1 0 0
0 0 1 1 0 0
0 1 0 1 0 0
0 1 1 0 1 0
1 0 0 1 0 0
1 0 1 0 1 0
1 1 0 0 1 0
1 1 1 1 1 1
I created 3 karnaugh maps and came up with the following boolean expressions
A'B'+A'C'+B'C'+ABC = Lt1
AB+AC+BC= Lt2
ABC = Lt3
(I hope I'm remembering this correctly)
Putting this all together I came up with 10 gates as written above (8 and gates and 2 or gates, using 3 inverters)
I'm not very good with flip flops or latches etc. Could there be a way of reducing the above further using these? I received half marks for this bonus question.
Help! I'm stumped! I've spent all weekend dwelling on this!!