# I need help with building a logic circuit in Logisim please

#### raziell122

Joined Mar 28, 2023
69
Hey everybody,
one of the sub-circuits in my mini project in logic design course needs to do an addition between two binary numbers, 4 bits each one, and then to display the result on 7-segment (Left digit and Right digit separately). I need to perform the addition only when "Level_Win" equals to '1'.
The difficult part for me is that the two numbers are coming from the same outputs (need to add between the previous number and the current number) depends on clock & Level_Win.
EDIT: in the circuit, MSB means right digit and LSB means left digit.
I tried to build the following circuit, but it does not work well:

Any ideas & tips to fix this are welcome!

#### dl324

Joined Mar 30, 2015
17,012
The difficult part for me is that the two numbers are coming from the same outputs (need to add between the previous number and the current number) depends on clock & Level_Win.
Can you elaborate on this? Are you saying that the two numbers you want to add are coming from the same source?

Have you thought about how your're going to display numbers larger than 9?

#### raziell122

Joined Mar 28, 2023
69
Can you elaborate on this? Are you saying that the two numbers you want to add are coming from the same source?

Have you thought about how your're going to display numbers larger than 9?
Yes of course I can, the two numbers MSB_Val & LSB_Val come from the following circuit:

which is a simple timer that counts from 19 down to 00.
The game is a maze game, and my goal is to add the two numbers MSB_Val + LSB_Val everytime the "Level_Win" input is '1' (which means the player has won and reached to the end of the maze) by using the former circuit that I posted up. There are 3 mazes in series so I have to save the former value of the addition result from level to level.
About your question, yes I guess that I will have to connect between Cout of LSB Adder to Cin of MSB Adder and to find a way to display it, but for now it does not even work for numbers that are lower than 9.
Please note: "Main_clock" is a clock with F=256HZ and Fclk1_128 is "Main_Clock" divided by 128.

#### dl324

Joined Mar 30, 2015
17,012
my goal is to add the two numbers MSB_Val + LSB_Val
You just input the two 4-bit numbers to a 4-bit adder.