RE: Cinematronics sound board behavior...

> Oh, I get it. Scenix is a device, not an operating system. ;-) It just
> sounds like another UNIX.
>
Heh.. I never noticed that. I can see where it would be confusing... ;-)

> > No Data Stack. (Passing variables to a subroutine is tricky for the
> > compiler and steals some of your RAM variable space.)
>
> Sounds like the 8051 C compilers.
>
> > Very limited RAM memory (don't even think of an array in RAM!,
> > like a pre-buffer for mixing!)
>
> Like the 8051!
>
Sorta. It's definately similar in the "it's a microcontroller" sense, but
memory is organized differently and the Scenix/PIC instruction set is really
different. (More RISC vs. the 8051's relative CISC-ness. Table lookups are
really shitty on small PIC type cores. You basically JSR to a byte that
loads the work register and then the next table entry is an RTS. Ugly.
Luckily this app won't need to do it except for addressing the samples in
memory...)

> It could do on-the-fly mixing. There's no reason to have a post-mix
> buffer. The only reason that's done now is because that's what all OS's
> want. A simple add+add+add+add+add/clip would work nicely (and does, I
> might add).
>
Yep. That's all the more I was thinking. (Hence the larger 10-12 bit DAC
"accumulator" from 8-bit samples.) I'm printing the Toshiba Smart Media
card datasheet as we speak to make sure I can pull data fast enough on the
fly. If not, a RAM buffer would be necessary which would pretty much
totally negate the benefit of the Scenix and I might as well just stick a
AD2181 DSP down...

> Why not use a Dallas 320? They're 3 clock and go up to 40MHZ! I don't know
> about pricing, though. We'd have to bankswitch the snot out of things, but
> I don't think it's all that evil.
>
Any fast little micro could probably pull it off. I picked the Scenix
'cause it's a good excuse to play with it and I already know the PIC
architecture well-- it also has CPU to burn (50 MIPS at 50MHz) so
bit-banging a DAC and talking to the serial access SmartMedia card is just a
"virtual peripheral" type of function. All the code and data memory is
internal and they're flash programmable which is nice.

-Clay
Received on Wed Jun 23 16:10:26 1999