4 Push Buttons for 4 Outputs with memory

[Toni]

Hi.

Recently I would like to do a circuit witch have 4 push buttons and select 4 independent outputs.

True table

S1 S2 S3 S4 O1 O2 O3 O4
------------------------------
1 0 0 0 1 0 0 0
0 1 0 0 0 1 0 0
0 0 1 0 0 0 1 0
0 0 0 1 0 0 0 1

How I can get this circuit?

Somebody can help me? Thanks.

Toni.

 

[Roff]

Do you want only one output to be active? In other words, if I4 is true, and I push S2, should I4 go off and I2 go on? I'm assuming this is what you want. Otherwise, you would need a reset button.

 

[Sebi]

The good old SAS560 IC (for TV channel select) do this exactly...
Or You can build some similar..

 

[stevez]

Why not connect S1 to O1, S2 to O2, etc. The table says that only one thing will turn O1 on - that's S1. The same can be said for O2 thru O4.

Is there a reason for other logic? The truth table doesn't address other combinations so does that mean there is some understood default behavior that isn't apparent? My knowledge in this area is limited but the lesson I recall is that 'don't care' is implied if not explicit in the table. Realise that my knowledge comes from one course a very long time ago.

 

[Roff]

Why not connect S1 to O1, S2 to O2, etc. The table says that only one thing will turn O1 on - that's S1. The same can be said for O2 thru O4.

Is there a reason for other logic? The truth table doesn't address other combinations so does that mean there is some understood default behavior that isn't apparent? My knowledge in this area is limited but the lesson I recall is that 'don't care' is implied if not explicit in the table. Realise that my knowledge comes from one course a very long time ago.

I think the title of the post has the answer - "with memory". My guess is that the pushbuttons are momentary (as most are).

 

[riad]

you should see electronique pratique nb 281 or 282 i guess
if you don't catch it i will attach it to the site

 

[stevez]

I guess I was focused on the apparent independence of switch/light combinations rather than the need for memory. I'll rephrase this into a question for the truth table that is presented - is there an implied relationship between anything other than S1/O1, S2/O2, S3/O3, S4/O4? I don't see one but as with other methods of notation, there might be assumptions that are understood by most others that aren't obvious to me.