I have a book that covers the AWE32. I'll get the ISBN and post it once I am back home.

It isn't by Creative so not sure if it includes the hardware stuff you are interested in but I will check.

There is "AWE32/EMU8000 Programmer’s Guide", google for emu8kpgm.pdf

Tiido wrote on 2021-09-28, 15:27:

There is "AWE32/EMU8000 Programmer’s Guide", google for emu8kpgm.pdf

"Goggle" my first message.

Then there is no further info, none of the MPU401 emulation info is ever disclosed. You can try to catch all the IO writes and log them, either from software or hardware and perhaps something sticks out. On early SB16 the IRQ and DMA selections are done in mixer registers, as seen here : http://www.earth.li/~tfm/oldpage/sb_mixer.html
It is probable the MPU emulation registers are placed into mixer space too.

I was digging for the same in a while, guess the following links may be of use to you:
Creative Sound Blaster AWE32 Developer Information Package
AWE32/EMU8000 Programmer’s Guide
The example of direct EMU8000 control (c) Grinus/ToM
The Un-official Sound Blaster AWE32 Programming Guide by Vince Vu a.k.a. Judge Dredd
X-BRAiN SB AWE Programming
It could also make sense to look at the available source code with EMU support (old sound libraries, players, games, linux kernel etc.)

That's the stuff that I partly told georgel about low level programming involving EMU8K. The "AWE32 Developer Information in PDF format" that is on the first link has high level functions related to MIDI emulation, but none of the links mentions anything related to NMI or MPU-401.

I checked the book I have and it is titled
AWE32: The Musician's Guide.
It has nothing at all about the hardware.