I am designing a 2-bit four function calculator. With separate modules for division, multiplication and add/subtract.
Subtraction is performed by adding 2’s complement to input. So I have 3 modules. These modules are gate based i.e. only AND,OR, NOT,XOR etc are used. I am using a 7-segment display to display output that means I also have a 7447 decoder.
I designed these three modules separately. i.e. on three isolated breadboards. In that phase I had separate decoders and 7-segments for each module
Now the circuit is complete and I have to merge the 3 modules in the following way.
There will be 4 inputs ( 2 numbers of 2-bits each) a0,a1, b0,b1.
A selection of function (add,subt,multiply,divide).
Output should be on 7-seg display
For a single module, I’d happily connect inputs, and outputs will go to decoder, and we have our nice 7 seg display powered up.
But how do I do this with 3 modules in a way that only the selected module gets the input and the output from only the selected module goes to decoder (and hence 7 segment display)? This diagram, I believe will help clarify the scenario.