Uploaded December 2022 | Updated September 2026, 3 weeks ago

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Displaying numbers is trickier than I expected! In this video we explore how to visualize the data inside of our simulated 4-bit registers, with the help of the double dabble algorithm and some seven segment displays.

Series playlist: youtube.com/playlist?list=PLFt_AvWsXl0dPhqVsKt1Ni_46ARyiCGSq
Simulation tool (work in progress): sebastian.itch.io/digital-logic-sim
Source code: github.com/SebLague/Digital-Logic-Sim
Support the channel: patreon.com/SebastianLague

Correction for a mistake in my boolean algebra explanation: youtube.com/watch?v=A-vLRThfJ4Q

Resources and Inspiration:
en.wikipedia.org/wiki/Double_dabble
electronics.stackexchange.com/questions/499884/3-digit-of-7-segment-on-logisim/499916#499916
pdf1.alldatasheet.com/datasheet-pdf/view/5697/MOTOROLA/SN54/74LS248.html

Music:
github.com/SebLague/Misc-Project-Info/blob/main/Digital-Logic-Sim/7Seg%20Music%20Credits.txt

Chapters
0:00 Intro
0:49 Two’s Complement Refresher
1:34 Seven-Segment Display + Truth Table
2:58 Boolean Algebra Basics
5:43 Simplifying the Equation
6:48 Converting Algebra to Logic Gates
8:33 Computer-Assisted Design
11:25 Testing the Digit Display Design
12:36 A Real-World Version (the 74LS248)
14:20 Visualizing the Data in a 4-bit Register
15:14 All Ten Digits
17:22 Binary Coded Decimal
19:49 The Double Dabble Algorithm
22:58 Dabbling with Logic Gates
24:05 Implementing Double Dabble
26:39 Displaying an 8-bit Number
27:18 Ripple Blanking
29:32 Displaying Negative Numbers
32:34 Testing the Final Design
33:50 Outro