Thank you for all the replies. I see some very interesting discussions and viewpoints. Here’s some history about my 8052 schematics:

Around 1996 I de-lidded a handful of different 8052 devices. I was surprised at how simple the layout was for the OKI 83C154 when compared to the other 8052s. It was the easiest to reverse engineer under the microscope. The geometries were large at 2 micron and only a single-metal layer. Using a low-resolution microscope camera, I captured pictures of the entire chip. For each section/block of the layout, I printed out pictures and taped them together. I then came up with a schematic for each block.

True, it’s very difficult to understand how the 8052 works when looking at just the schematics. This is where a digital simulator comes in. I used Orcad VST (old DOS stuff). To begin with, I simulated just the most critical blocks: Instruction Decoder, PLA, Accumulator, ALU and Program Counter. Other blocks were added later. I first made sure I could execute very simple programs like:

INC A
INC A
INC A

Obviously, you need to know basic stuff like, an INC A instruction uses 1 machine cycle. Each machine cycle use 6 system clocks. Stuff like this is spelled out in the data book.

It was a part-time project. It was not a painful effort at all. It was fun. By 1997, I was simulating the entire 8052. It was very satisfying to get to this point.

In 1998 I decided to fabricate my own 8052 design though MOSIS. Yet another part-time project. Eventually, came up with a complete redesign, not a copy. It runs 3 times faster than original design.
Please check out: www.satre-electronics.com/home/personal-projects

Cheers,
Scot