[sdiy] dsPIC33 question..

[Eric Brombaugh]

karl dalen wrote:

> Btw a ARM7 has way more DSP power then an dsPIC.

I disagree.

First let me preface this - I've used both in pro applications (ie - I 
got paid to do the work) and I like both. I wouldn't try to use the ARM 
for high-performance DSP though, and I wouldn't use the dsPIC for 
complex low-power applications.

ARM7 is a great processor for large embedded projects. You can do a lot 
with them and they're very inexpensive. The architecture supports a lot 
of memory and typically they have very low power operating modes. 32-bit 
native data format is great for high resolution math operations. When it 
comes to DSP however they're seriously lacking in areas where the dsPIC 
has better resources.

dsPIC has a true MAC with complex addressing modes (dual-access data 
buses, prefetching, pointer updating, etc) which enable single-cycle 
operations on FIR and IIR filters. dsPIC can execute from flash at full 
speed - most ARM7s need complex caching and Thumb code to do this. ARM7 
has fairly complex interrupt processing overhead while dsPIC has 
interrupt vectoring built in to the heart of its execution unit which 
enables very fast response.

Bottom line: each processor has its strengths. While you can do DSP on 
an ARM7, the dsPIC can do many (not all) kinds of DSP better than an ARM7.

If you need high-resolution, high-speed DSP for things like hi-fi audio, 
video or radio applications, you probably shouldn't be considering 
either of these though.

Eric