Pi GPIO Register
From SpecNext official Wiki
| Number | $98-$9B |
|---|---|
| Readable | Yes |
| Writable | Yes |
| Short Description | GPIO pins mapped to Next Register |
Bits 27-0: Read / Write the GPIO pin state (soft reset = $00001FF)
Writes only propagate when the corresponding pin has its output enabled in Pi GPIO Output Enable Register ($90-$93).
The register $9B is MSB (most significant byte = bits/pins 31-24), register $98 is LSB (least significant byte = bits/pins 7-0).
Bits 31-28 are not explicitly specified in the docs, so consider them "Reserved, use 0".
(note: Next registers with number higher than $7F are inaccessible from Copper code)