Breadboard Calculator

After taking a Computer Architecture course, I became very interested in further understanding how computers work on a hardware level. At this point, I had an excellent understanding of how to write code across many different languages, but knew little of how the computer understands and executes this code. I decided to begin building an 8-bit, breadboard calculator that serves as the core of a basic computer.

The computer is split into modules, where each breadboard performs a distinct function

The top module is an adjustable frequency clock that can also be set to manual mode
Next is the ‘A’ register that feeds into the ALU. The LEDs allow for monitoring the present value
In the middle is the heart of the ALU, the XOR logic gates. These can be set to addition and subtraction mode. The ‘A’ and ‘B’ register feed in to produce the output value.
Second to last is the ‘B’ register. It behaves identically to ‘A’.
The left most, vertical board is the common bus. Each register and the ALU connect to his bus. Their individual access to this bus is controlled by a transceiver.
Finally, the bottom cell displays output values. The EEPROM chip next to the 7-segment displays contains encodings for the 256 possible ALU outputs. Based on the binary output, the EEPROM correctly displays the corresponding decimal value.