Pls i'm a newbie to circuit design. I'll like to design a calculator that can perform only addition and substraction using decoders, encoders, 7 segment display(displays only result), adder/substractor IC.
Pls for a start, I need helpful suggestion and recommendation

 

Welcome to AAC!

I'd start by researching ALUs.

 

I just want to be clear this is a combinational circuit right, not a sequential one where you enter the number and then an operation and then a number so that calculator has to "remember" the state? You didn't state you are using registers or flip-flops so I will assume this is not a sequential circuit.

If it is a combinational circuit (the easier of the two), first start by defining your inputs and outputs. Questions you want to ask yourself:

• What kinds of numbers will you allow? Are they input in binary or decimal? How big are they going to be?
• Do you have a good understanding of Two's Complement Arithmetic? With that you'll see that an addition and subtraction unit is basically the same thing
• If you already have an IC for adder/subtractor do you understand all its inputs and outputs?

 

The post title is a little confusing, Ladder Logic usually infers Boolean arithmetic?
Max.

 

I mean that I fully understand the concept of the Adder/Subtractor circuit and that I will like to use the idea to create a very simple circuit that can add/subtract a 4 bit number and give a bit result (at least for beginning).
I plan using an 16 to 4 line encoder for encoding inputs from the buttons, these encoded inputs is then added or subtracted (based on user input) and the result finally decoded to give an output.
I really dont Know how to incoperate a sequential circuit to the input states in order to remember user input. Also I dont know how to implement the project without it been able to remember user input (combinational circuits)
Please I need suggestion or additions on how best to achieve this.