The output register is similar to any other register (like the A and B registers) except rather than displaying its contents in binary on 8 LEDs, it displays its contents in decimal on a 7-segment display. Doing that requires some complex logic; luckily there’s an easier way:

Videos

Schematic

(coming soon!)

Parts list

QuantityDescription
2Breadboard
11kΩ resistor
1100kΩ resistor
20.01µF capacitor
1555 timer IC
174LS08 (Quad AND gate)
174LS76 (Dual JK flip-flop)
174LS139 (Dual 2-line to 4-line decoder)
174LS273 (Octal D flip-flop)
128C16 EEPROM
4Common cathode 7-segment display

Additionally, I used an Arduino Nano, two 74HC595 shift registers, and one more breadboard to build a simple EEPROM programmer to program the 28C16 EEPROMs.