Ben Eater

Digital logic gets really interesting when we connect the output of gates back to an input. The SR latch is one of the most basic memory circuits that we can build on to make counters, registers, and all sorts of other interesting things. Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. Complete parts list (everything in this video): 1x 74LS32 (Quad two-input OR gate) 1x 74LS02 (Quad two-input NOR gate) 3x 330Ω resistor 3x Momentary "Microtivity 6mm tact switch" 3x LEDs Solderless breadboard(s) 22 gauge wire USB charger and cable or some other 5v power source

Building on the SR latch from the previous video (https://youtu.be/KM0DdEaY5sY), the D latch makes it easier to store a single bit of data. Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. Complete parts list (everything in this video): 4x 74LS02 (Quad two-input NOR gate) 2x 74LS08 (Quad two-input AND gate) 8x 330Ω resistor 1x 1kΩ resistor 8x Momentary "Microtivity 6mm tact switch" 9x LEDs Solderless breadboard(s) 22 gauge wire USB charger and cable or some other 5v power source

Building on the D latch from the previous video (https://youtu.be/peCh_859q7Q), the D flip-flop has a "clock" input instead of an "enable" input and stores data just on the rising edge of the clock. Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. Complete parts list (everything in this video): 1x 74LS02 (Quad two-input NOR gate) 1x 74LS08 (Quad two-input AND gate) 2x 330Ω resistor 1x 1kΩ resistor 1x 0.1µF capacitor 2x Momentary "Microtivity 6mm tact switch" 4x LEDs Solderless breadboard(s) 22 gauge wire USB charger and cable or some other 5v power source

An update on my plans to build another 8-bit computer from scratch and make videos of the whole process! Buy a kit and build your own! https://eater.net/8bit/kits Support me on Patreon: https://www.patreon.com/beneater

Our computer's clock is built using several 555 timers. The first is configured as an astable oscillator. See https://eater.net/bbcpu8-clock-module for more. Part 2: https://youtu.be/81BgFhm2vz8 Part 3: https://youtu.be/WCwJNnx36Rk Part 4: https://youtu.be/SmQ5K7UQPMM Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. Complete parts list (everything in this video): 1x 555 timer IC 1x 1MΩ potentiometer 2x 1kΩ resistors 1x 100kΩ resistor 1x 330Ω resistor 1x 2µF capacitor 1x 0.1µF capacitor 1x 0.01µF capacitor 1x LED Solderless breadboard 22 gauge wire USB charger and cable or some other 5v power source

Our computer's clock is built using several 555 timers. The second is configured as a basic monostable circuit to debounce a pushbutton. See https://eater.net/bbcpu8-clock-module for more. Part 1: https://youtu.be/kRlSFm519Bo Part 3: https://youtu.be/WCwJNnx36Rk Part 4: https://youtu.be/SmQ5K7UQPMM Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. Complete parts list (everything in this video): - Circuit from part 1 - 1x 555 timer IC - 1x 1kΩ resistor - 1x 1MΩ resistor - 1x 330Ω resistor - 1x 2µF capacitor - 1x 0.1µF capacitor - 1x 0.01µF capacitor - 1x Momentary "Microtivity 6mm tact switch" - 1x LED - 22 gauge wire

Our computer's clock is built using several 555 timers. The second is configured as a bistable multivibrator to debounce the toggle switch for selecting between the clock oscillator and manual clock stepping. See https://eater.net/bbcpu8-clock-module for more. Part 1: https://youtu.be/kRlSFm519Bo Part 2: https://youtu.be/81BgFhm2vz8 Part 4: https://youtu.be/SmQ5K7UQPMM Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. Complete parts list (everything in this video): - Circuit from parts 1 and 2 - 1x 555 timer IC - 2x 1kΩ resistors - 1x 330Ω resistor - 1x 0.01µF capacitor - 1x Double-pole toggle switch - 1x LED - 22 gauge wire

Our computer's clock is built using several 555 timers. This video covers the logic that ties them together, resulting in the completed clock module. See https://eater.net/bbcpu8-clock-module for more. Part 1: https://youtu.be/kRlSFm519Bo Part 2: https://youtu.be/81BgFhm2vz8 Part 3: https://youtu.be/WCwJNnx36Rk Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. Complete parts list (everything in this video): - Circuit from parts 1, 2, and 3 - 1x 74LS04 (Hex inverter) - 1x 74LS08 (Quad AND gate) - 1x 74LS32 (Quad OR gate) - 1x LED - 22 gauge wire

Before we build the registers for our 8-bit computer, this video describes the basic operation of the bus and how data moves from one module to another across the bus. See https://eater.net/bbcpu8-registers for more. Support me on Patreon: https://www.patreon.com/beneater

With tri-state logic, a logic gate can be effectively disconnected from the circuit rather than assuming the normal 0 and 1 logic levels. This video goes into more detail on what it means to output a 0 or 1 and then describes how and why we'd want to output neither. This detail is essential to how a bus works. Support me on Patreon: https://www.patreon.com/beneater See https://eater.net/bbcpu8-registers for more.

Before we build the 8-bit registers for our computer, let's design and build a 1-bit register. The 8-bit registers we'll actually use in our 8-bit computer will be simplified. We're going to take a big shortcut—using the 74LS173—described at the end of this video. But before we get to that, this video shows how we could build a 1-bit register using more basic components. Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. See https://eater.net/bbcpu8-registers for more. Complete parts list (everything in this video): - Clock circuit from https://youtu.be/SmQ5K7UQPMM - 1x 74LS04 (Hex inverter) - 1x 74LS08 (Quad AND gate) - 1x 74LS32 (Quad OR gate) - 1x 74LS74 (Dual D flip-flop) - 1x LED - 22 gauge wire - 5 volt power source (e.g., a USB phone charger)

In this video, we'll build the first of three 8-bit registers used in the 8-bit computer! Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. See https://eater.net/bbcpu8-registers for more. Complete parts list (everything in this video): - 2x 74LS173 (4-bit D-type register) - 1x 74LS245 (Octal bus transceiver) - 8x LED - 22 gauge wire - 5 volt power source (e.g., a USB phone charger) (The computer will have 3 registers like this; see the next video for details)

In this video, we test the register we built in the last video (https://youtu.be/CiMaWbz_6E8) and connect it to two more registers like it. After this video, we'll have three registers built and tested: - A register - B register - Instruction register Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. See https://eater.net/bbcpu8-registers for more. Complete parts list (everything in this video): - Clock circuit from https://youtu.be/SmQ5K7UQPMM - 6x 74LS173 (4-bit D-type register) - 3x 74LS245 (Octal bus transceiver) - 32x LEDs - 22 gauge wire - 5 volt power source (e.g., a USB phone charger)

How can we represent negative numbers in binary? There are several ways. This video compares using a sign bit, ones complement, and twos complement. Twos complement is the most commonly technique because it's relatively easy to implement in hardware and it makes addition and subtraction with negative numbers easy. Support me on Patreon: https://www.patreon.com/beneater

In this video we go over the design for the Arithmetic and Logic Unit for our 8-bit computer. Before watching it's helpful to understand: - How a binary adder works: https://www.youtube.com/watch?v=wvJc9CZcvBc - How negative numbers are represented in binary: https://www.youtube.com/watch?v=4qH4unVtJkE Support me on Patreon: https://www.patreon.com/beneater See https://eater.net/bbcpu8-alu for more.

In this video, we'll build the ALU for our 8-bit computer! Support me on Patreon: https://www.patreon.com/beneater See https://eater.net/bbcpu8-alu for more. You can get all the components used in this video from any online electronic components distributor for a few dollars. Complete parts list (everything in this video): - 2x 74LS283 (4-bit binary full adder) - 2x 74LS86 (Quad XOR gate) - 1x 74LS245 (Octal bus transceiver) - 8x LED - 22 gauge wire - 5 volt power source (e.g., a USB phone charger) - Clock module and registers from previous videos

When we built and powered up the ALU for our 8-bit computer in the last video (https://youtu.be/S-3fXU3FZQc), it didn’t work properly. In this video we’ll try to get to the bottom of what’s going on. I got lucky that the problems were relatively easy to find. Sometimes troubleshooting can take a lot more time and be a lot more frustrating. But it’s also often where you learn the most. Sometimes you’ve just made a silly mistake (that you keep overlooking). Sometimes you get stuck because of some detail you don’t know about *yet*. It’s important to remember that unless you completely give up, you *will* eventually figure it out. There are a lot of resources out there to help you. Sometimes just taking a break and coming back to it a few days later with fresh eyes does wonders. Support me on Patreon: https://www.patreon.com/beneater See https://eater.net/bbcpu8-alu for more.

In this video, we test the ALU we built (and fixed) in the last two videos (https://youtu.be/S-3fXU3FZQc and https://youtu.be/U7Q8-2YZTUU) and connect it to the bus. See https://eater.net/bbcpu8-alu for more. Support me on Patreon: https://www.patreon.com/beneater

An introduction to the 16-byte by 8-bit static RAM that we're going to build for our 8-bit computer. Support me on Patreon: https://www.patreon.com/beneater Previously we built a 1-bit register: https://youtu.be/-arYx_oVIj8 Next we extended that to build an 8-bit register: https://youtu.be/CiMaWbz_6E8 In this video, we extend that further to describe how a 16-byte static RAM would work. Then we take a look at the 74LS189, which we'll use to build our computer's RAM. See https://eater.net/bbcpu8-ram for more.

Part 1 of building the RAM module for the 8-bit computer. Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor for a few dollars. See https://eater.net/bbcpu8-ram for more. Complete parts list (everything in the RAM module): - 2x 74LS189 (64-bit random access memory) - 2x 74LS04 (Hex inverter) - 1x 74LS173 (4-bit D-type register) - 4x 74LS157 (Quad 2-to-1 line data selector) - 1x 74LS245 (Octal bus transceiver) - 1x 74LS00 (Quad NAND gate) - 14x LEDs (9 red, 4 yellow, 1 green) - 3x 1KΩ resistors - 1x 0.01µF capacitor - 22 gauge wire - 5 volt power source (e.g., a USB phone charger)

Part 2 of building the RAM module for the 8-bit computer. In this video, we add the memory address register (MAR) and DIP switches for setting the address when programming along with the logic to switch between using the register and using the switches. Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor (Jameco, Digikey, Mouser, etc). See https://eater.net/bbcpu8-ram for more. Complete parts list (everything in the RAM module): - 2x 74LS189 (64-bit random access memory) - 2x 74LS04 (Hex inverter) - 1x 74LS173 (4-bit D-type register) - 4x 74LS157 (Quad 2-to-1 line data selector) - 1x 74LS245 (Octal bus transceiver) - 1x 74LS00 (Quad NAND gate) - 14x LEDs (9 red, 4 yellow, 1 green) - 3x 1KΩ resistors - 1x 0.01µF capacitor - 22 gauge wire - 5 volt power source (e.g., a USB phone charger)

Part 3 of building the RAM module for the 8-bit computer. In this video, we add the DIP switches and logic for manually inputting data in program mode. In run mode, data can be written from the bus into RAM. Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor (Jameco, Digikey, Mouser, etc). See https://eater.net/bbcpu8-ram for more. Complete parts list (everything in the RAM module): - 2x 74LS189 (64-bit random access memory) - 2x 74LS04 (Hex inverter) - 1x 74LS173 (4-bit D-type register) - 4x 74LS157 (Quad 2-to-1 line data selector) - 1x 74LS245 (Octal bus transceiver) - 1x 74LS00 (Quad NAND gate) - 14x LEDs (9 red, 4 yellow, 1 green) - 3x 1KΩ resistors - 1x 0.01µF capacitor - 22 gauge wire - 5 volt power source (e.g., a USB phone charger)

Testing and troubleshooting the RAM module. In this video we check out the RAM module, fix an issue, and make a small modification so RAM writes are triggered on the rising edge of the clock. Support me on Patreon: https://www.patreon.com/beneater You can get all the components used in this video from any online electronic components distributor (Jameco, Digikey, Mouser, etc). See https://eater.net/bbcpu8-ram for more. Complete parts list (everything in the RAM module): - 2x 74LS189 (64-bit random access memory) - 2x 74LS04 (Hex inverter) - 1x 74LS173 (4-bit D-type register) - 4x 74LS157 (Quad 2-to-1 line data selector) - 1x 74LS245 (Octal bus transceiver) - 1x 74LS00 (Quad NAND gate) - 14x LEDs (9 red, 4 yellow, 1 green) - 3x 1KΩ resistors - 1x 0.01µF capacitor - 22 gauge wire - 5 volt power source (e.g., a USB phone charger)

Check out my SR latch video first: https://youtu.be/KM0DdEaY5sY The JK flip-flop builds on the SR flip-flop by adding a "toggle" function when both inputs are 1. The S (set) and R (reset) inputs are now referred to as J (set) and K (reset) to indicate the different operation. In other words: J=1, K=0 sets the flip-flop J=0, K=1 resets the flip-flop J=1, K=1 toggles the flip-flop The toggling function is useful for building counter circuits which we'll do in future videos. Support me on Patreon: https://www.patreon.com/beneater