My evil modular plans -- DSP

[Mikko Helin]

   It seems indeed that SHARC (ADSP-21060) is fine DSP for digital
   synthesis as it's got 4 Mbit of dual-port RAM internal RAM AND
   it's modular thanks to it's SHARCPAC interface for interprocessor
   communication. Visit ADI's homepage at

   http://www.analog.com/products/sheets/ADSP21060.html 

   for more information. Does anybody know how much man has to
   pay for ADSP-210XX EZKIT (combines 16-bit ISA card and
   software, includes AD1847 CODEC, but any other can be used
   through modular analog from end MAFE)?

   -Mikko

   ---------------------------------------------------------------
>
>   DSP's are not that expensive now, but you may like to implement
>   more than one module with one DSP. So you need some patching
>   inside a module, and when you are going to expand your system
>   you may want patch one function on DSP 1 to another on DSP 2,
>   so you'll come to decision to use a common shared bus. I think
>   it's best done with physically shared RAM and with an operating
>   system that treats all modules inside a DSP as separate processes
>   which get their input from OS scheduler - a process which looks
>   for messages sent to special process (like VCF) containing data
>   to be processed. OS patching system then decides where that data
>   is then sent next. I'm not sure if OS is needed at all, if
>   every process has it's own dedicated data input and data output buffers,
>   propably ping-pong style dual-port RAMs (or conventional RAM
>   with flags). Then it's only question of knowing which address
>   to use for input and which one for output, and some timing
>   information is needed, at least a flag which tells when it's
>   ok to read or write data. D/A is then the last module process
>   which then simply sends it's input data through serial port
>   to DAC, which may be CS433x series or better one. Between
>   DSPs real dual-port RAMs are needed anyway (visit
>   www.qualitysemi.com for more information). If data format
>   is fixed between and inside DSPs, whether it's integer, fixed
>   or floating point, and (dual-port RAM) interface is defined
>   I guess different DSPs can be mixed.
>
>   But if you limit one DSP for one function at a time, it's
>   easiest to use digital signals without A/D & D/A between,
>   simply connect (buffered!) sample clock, sample data and word clock
>   signals like in analog system, and derive all clocks from a
>   common master clock to avoid EMI. There may be problems with
>   jitter if clocks are chained too long.
>
>   Just some thoughts,
>
>   -Mikko
>