How can machine code actually create electric signals to turn transistors on and off?

Question

I’m a junior EE student, but I’m still genuinely confused about this, and other answers still haven’t cleared my confusion. How can voltages be manipulated by code in a digital circuit without someone physically closing and opening circuit connections?

In: Engineering

Answer 1

Ben Eater has a fantastic series on building a breadboard computer from scratch: https://www.youtube.com/playlist?list=PLowKtXNTBypGqImE405J2565dvjafglHU

To answer your question, the first part of each instruction is called the “op code.” This code goes into a decoder which translates the binary value into several control lines. E.g. code 100 (4) turns on the memory address lines, turns on the adder input buffer, and turns off the display input buffer. Think of it like a lookup table of different “recipes” which trigger different actions inside the computer.