Analysing the MC14500B Discrete Clone

A project log for One Bit CPUs

I have been exploring one bit CPUs. For the right application they may be worth knowing.

agpcooperagp.cooper 08/12/2017 at 15:450 Comments

Pulling the MC14500B Discrete Clone apart and putting it back together

In case you have not seen it, here is the video demonstrating the MC14500B clone:

Here is the clone schematic:

I have found that the clock logic is glitched and have edited the schematic:

The actual MC15400B has the instruction latched but this is only necessary if the ROM space is interlaced with the input or output address. The clone also differs in that the Data signal has been split into Din and Dout. This is actually more convenient. Finally NOPO 0 and FLAG 0 have not been decoded. The on board clock is also absent.

Here is the MC14500B block diagram and pin assignment for reference:

Finally here is the Instruction Set:

A working Example

Here is a working example of the MC14500B by Nicola Cimmino:

He has also put his schematic and other data on github:


In this case, he uses an Arduino to program the SRAM.


And finally an ultra simple version where the operator is the ROM :(

And his video and schematic: