That's what sheet 4 shows I believe. Counter wraps from 0 and the wrap cascades through causing a toggle of SNDSRC and also causing an async reset (in effect loading the counter with the reg'd value, which due to nor gate & reset use looks to only work correctly when the counter has wrapped to all 1's).
If I've read the schematics correctly and you load FE06 with 0. It should in effect get a tick @ 125kHz which will cause it to wrap to 255, toggle the SNDSRC and immediately cause a reset of the counter back to 0, which occurs before the next tick, so every tick causes a SNDSRC toggle, producing in effect the 62.5kHz maximum frequency the AUG notes.
That's also how my implementation works too. However, using SOUND with values in the 0..255 range produce wildly different results to poking at the register itself and I'm at a bit of a loss as to explain why.
Do you hear similar sound tones using SOUND with 0 and 255 as you would loading the register directly with 0 and 255 (the two might be reversed)?
On another _note_ (pun intended
) if you look at the frequencies for middle C on this page
The B below middle C is 246Hz which is close to the lower limit the AUG notes the electron can produce, 244Hz. Yet Page 118 of the user guide has a whole octave of notes below what they highlight as middle C "52". That doesn't make sense does it?
If "4" is actually middle C, then I guess that would tally up with what I'm seeing in my implementation, but then my audio sounds quite different to the youtube videos I've listened to. As though it's nearly an octave too high.