[AH] Re: [sdiy] TB-303 cpu question - impossible

[Colin f]

> I quote from the Oakley 3031 documentation ..
> 
> In the TB303 the slide function is always triggered prior to any
> new note. This was not really by design, more of a by-product due to 
> cost saving.

What this means is the the slide circuit is activated as every note is
written to the DAC.
It is triggered *immediately* before.

There is a single line that strobes the DAC and enables the slide circuit.
The DAC only needs a positive edge to trigger, so the designers used the
edge of the control signal to load the DAC, then the line stays high if
slide is to be enabled.
This means that the slide circuit is always 'blipped' as every note is
loaded into the DAC.

There is absolutely no slide premonition on the 303.
I extract the CPU signals directly for my MidiBass MIDI interface, so I know
exactly what is going on.

One interesting quirk, that probably shows something of how simple the 303
code is, is that the DAC value for a note is written at every beat, even if
the same note is being held over. No point wasting a conditional test in a 4
bit CPU with 1000 bytes of code space.
Even if they had wanted slide 'in advance', I doubt the CPU could have
managed it.

Cheers,
Colin f