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This is my build of Ben Eater's 8-bit breadboard computer
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Replaced original 3 digit display with the 4 Digit display designed by Be Eater. The display is using a 4 Digit in one package Anode type with P-Channel Mosfet transistors to drive the Display.
Latest commit 3dc8388 Apr 14, 2017


This is my build of Ben Eater's 8-bit breadboard computer. Posted videos of my Build.

Ben Eater's 8 Bit computer videos. Building an 8-bit breadboard computer!

Ben Eater SAP 8-bit computer diagram 4-9-2017.vsd This is a MS Office Visio file (.vsd). You can get a Visio viewer if you don't have Visio. I included an XPS file format as well. Using the Visio file you will find it helpful when building it as you can highlight a connection line and it will show you the two connection points.

List of Issues encounter building the computer

Adder Circuit 3-10-2017 ( Reversed Data Lines )

Clock Circuit 3-13-2017 (1 MEG Resistor connected to 5v not Ground)

Clock Circuit – Debounce adjustment need .5 second delay ( 1uf x 470K = 470ms)

MAR MI Address Lines reversed

PC – Added Clear Signal

OP Code – Reset was tide to HIGH Causing count to 7 not 5

Added Reset Buttons

RI needs to be High to Write to RAM, Since a NAND gate inverts the signal w/Clock

Corrected Jump Circuit Only One Nand gate IC ( 4 Nand Gates Used)

Fixed RAM Write issue - Needed to isolate the clock from the RC circuit. Fixed feedback noise.

Added 10K Resistor to Write button in Program Mode (Pull-up to 5 v instead of Floating)

Added RC Circuit to absorb spikes during switching between Run and Program mode. (Not in Picture but in Diagram) This Fixed issue where switching between Run and Program mode caused Memory Write signal to go low clearing RAM contents.

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