Reconfiguration, Spartan 3, Compressed bit stream, ICAP

I am working on a consumer product development. We have decided to use
the Spartan 3 FPGA. But to keep the cost down, we want to use  a very
small PROM on the board. How could I program the Spartan 3 FPGA with a
tiny PROM?

I was thinking of creating a compressed bitstream for the small
processor interface logic that will take hardly 5 to 10% of the
slices(that should lead to good compression ratios so as to fit in a
tiny PROM) and then use this logic to self configure the new bitstream
file from the processor interface and the FPGA having an external
interface to talk to itself using selectMAP port (since  Spartan 3
does not have any ICAP module).

But I have many questions:
1. First of all, does Spartan 3 at all support self/dynamic
reconfiguation as my microprocessor interface inside the FPGA has to
keep working to configure the FPGA? So Spartan3 partial
reconfiguration should not affect my functionality.
2. I know there is a option called compressed bitstream. Is it
possible to use compressed bitstream from the PROM at the powerup? I
did not notice any decompression engine in the spart3 documentation. I
need to use the compressed bitstream at the startup because I want to
use the small PROM, but the partial reconfiguraton requires that very
first configuration should be of full bit stream. So I need to have a
tiny bitstream that can be loaded in the PROM, and used by the
Spartan3 for the first time configuration.

Thank you
~Naveen

naveen_jain86@hotmail.com (video1) wrote in message news:<b29aaa65.0309181138.1ffed2ad@posting.google.com>...
> I am working on a consumer product development. We have decided to use
> the Spartan 3 FPGA. But to keep the cost down, we want to use  a very
> small PROM on the board. How could I program the Spartan 3 FPGA with a
> tiny PROM?
> 
> I was thinking of creating a compressed bitstream for the small
> processor interface logic that will take hardly 5 to 10% of the
> slices(that should lead to good compression ratios so as to fit in a
> tiny PROM) and then use this logic to self configure the new bitstream
> file from the processor interface and the FPGA having an external
> interface to talk to itself using selectMAP port (since  Spartan 3
> does not have any ICAP module).

read the postings - S3 logic (your tiny cpu) is not active during 
reconfiguration, at least what I understood what xilinx had to say :(

antti

are you sure that Spartan 3 can not configure itself? 

antti@case2000.com (Antti Lukats) wrote in message news:<80a3aea5.0309182129.63dad53a@posting.google.com>...
> naveen_jain86@hotmail.com (video1) wrote in message news:<b29aaa65.0309181138.1ffed2ad@posting.google.com>...
> > I am working on a consumer product development. We have decided to use
> > the Spartan 3 FPGA. But to keep the cost down, we want to use  a very
> > small PROM on the board. How could I program the Spartan 3 FPGA with a
> > tiny PROM?
> > 
> > I was thinking of creating a compressed bitstream for the small
> > processor interface logic that will take hardly 5 to 10% of the
> > slices(that should lead to good compression ratios so as to fit in a
> > tiny PROM) and then use this logic to self configure the new bitstream
> > file from the processor interface and the FPGA having an external
> > interface to talk to itself using selectMAP port (since  Spartan 3
> > does not have any ICAP module).
> 
> read the postings - S3 logic (your tiny cpu) is not active during 
> reconfiguration, at least what I understood what xilinx had to say :(
> 
> antti

Maybe you should put a little PIC on the board just for configuration. That
way you could use regular compression on the bitstream and put a smaller
prom on the board and save money. The Spartan 3 supports partial
configuration. Remember that the JTAG port is always live.

If you can afford some consulting I can port some code to your system.

Steve