I am trying to find a way to add four 4-bit binary numbers to a 16-bit shift register, one(group of 4 bits) by one. This way I can store 4 decimal numbers(0-9) in the register, adding them by pushing 1 of 10 buttons labeled from "0" to "9"(simple push buttons).
I thought of something but I think it's wrong:
Step one: load 4-bit data
Step two: shift them four times
Step three: load 4-bit data again
But the simulator say it does not know the values of the shifted bits.
Another way would be adding the numbers bit by bit, using only the "shift" and the "input pin", but it won't be easy since there's a clock.
What is the best way of doing it?