[sdiy] Organisation of tasks in synth's main uP

[grant at musictechnologiesgroup.com]

> pro-question time: in assembly, I rely heavily on the overflow bit  
> being set to detect wrap-around, e.g. in 8-bit registers.  But these  
> days I program mainly in C and I can't figure out how to access that  
> overflow bit.
> I have gone so far as to use 7-bit numbers and treat the MSB as an  
> overflow, but does anyone know how to read the CPU's overflow bit from  
> C?

Admittedly it hurts at first moving to C (and procedural methods). I
don't think you want to look at the overflow bit. It's too hardware and
compiler dependent. The nice thing about C, when used "properly" is that
the code really is quite portable.  I think in order to really benefit
from C you need to allow yourself to accept the spirit of it. Same goes
for C++ -- if you don't adopt the spirit you just keep writing C and
missing out on the great benefits.  So I would say to try and think at a
slightly higher level. "There are no CPU flags". The penalty is minimal
and the benefits huge. Just use a for or while loop and get creative
with the start and/or end conditions. If that's not intuitive try moving
up to an unsigned int or doing an extra C statement before or after the
loop.  Using an unsigned int now and then shouldn't be a barrier. If
it's a local variable the compiler will recapture the variable space and
the difference in execution speed probably one uS. I also try to avoid
being "too clever".  If it's hard to understand now, it will be way hard
later when you go back to revisit that code.

GB