Schematics

Here are the complete schematics of the LEO-1 system in PNG format and also as a downloadable zip of ExpressSCH files. I am not sharing the PCB layout files because a few of the boards had errors that needed some trace cutting and rewiring.

Memory Unit



Address Decoding


Real Time Clock


I/O Ports


DIP switches


ZIF sockets


Expansion 1


Expansion 2


ROM 0


ROM 1


ROM 2


ROM 3


LED 1


LED 2


LED 3


RAM 0


RAM 1


RAM 2


RAM 3


RAM 4


RAM 5


Power


Connectors

Control Unit



Clock


Decoding


Program
Counter


Instruction
Register


Bank Registers


ALU-B input
high


ALU-B input
low


Address bus high


Address bus low


Bus hold &
Mux high 1


Bus hold &
Mux high 2


Bus hold &
Mux low 1


Bus hold &
Mux low 2


LED 1


LED 2


LED 3


LED 4


Power


Connectors 1


Connectors 2

Register Unit



Register R0


Register R1


Register R2


Register R3


Register R4


Register R5


Register R6


Register R7


Control


LED 1


LED 2


LED 3


LED 4


Power


Connectors

Arithmetic and Logic Unit



Adder


AND


OR


XOR


B/SB


Shift In


Shift


Shift Out


Decoding


LED 1


LED 2


LED 3


LED 4


Power


Connectors

Miscellaneous



Digits
(not yet verified
as correct)


Front Panel