Configuration of Spartan 3 devices

Antti wrote:
> Falk Brunner schrieb:
>
> > Antti schrieb:
> >
> > > well the OP wanted S3 so thats not an option,
> >
> > Is it? Says who? I did not hear anything from the OP that prevents the
> > use of a S3E. There are many ways to skin a cat. ;-)
> >
> > Regardas
> > Falk
>
> OP wanted solution for S3, not for S3e
> for S3e the SPI flash is obvious, and I bet Xilinx FAE would have
> suggested it, so I must assume that the S3e wasnt an option
> and solution was really required for S3
>
> equally well I could say that solution is to use Cyclone or LatticeEC
> PFGA's
> as both support SPI loading and are comparable in size to Spartan-3, eg
> larger than larger device in Spartan3e

Do the S3e parts have the same issue with the overly stiff pullups that
the S3 parts have?  I'm not sure if they are going to fix that in the
S3a parts or not.

Hello,

It is correct that S3E is easier to configure using an SPI flash.
Because S3 devices have more IOs than S3E I have to use S3 for this
design.

Thanks for the info,
Dolphin

"rickman" <gnuarm@gmail.com> wrote in message 
news:1159365978.100646.5140@i42g2000cwa.googlegroups.com...
>
> Do the S3e parts have the same issue with the overly stiff pullups that
> the S3 parts have?  I'm not sure if they are going to fix that in the
> S3a parts or not.

It was fixed, indeed.  The pullups on the S3s were pretty stiff.  Things are 
back toward expectations now with the S3E.  I would expect the S3A to follow 
S3E's lead. 

John_H wrote:
> "rickman" <gnuarm@gmail.com> wrote in message
> news:1159365978.100646.5140@i42g2000cwa.googlegroups.com...
> >
> > Do the S3e parts have the same issue with the overly stiff pullups that
> > the S3 parts have?  I'm not sure if they are going to fix that in the
> > S3a parts or not.
>
> It was fixed, indeed.  The pullups on the S3s were pretty stiff.  Things are
> back toward expectations now with the S3E.  I would expect the S3A to follow
> S3E's lead.

Fixed is a relative term.  Worst case for the S3 is 1.4 kohms while the
Virtex 4 is 16.5 kohms.  The S3E is between at 2.7 kohms, only about 2x
the S3 value and under a fifth of the V4 value.  I can only assume that
there is some issue with the IO design in the Spartan series that makes
it hard to get a realisticly useful pullup value around 20 kohms like
the V4 and other Xilinx product use.  I'm sure we will never know the
reason why.

Dolphin wrote:

>Hello,
>
>I am considering to use Spartan 3 devices on our new board. Xilinx
>recommends XCF04S and XCF08P devices for configuration of a Spartan 3
>1000. Does anybody know other and cheaper configuration solutions for
>this FPGA?
>  
>
Well, I'm always behind the curve on this stuff, but SST has some VERY
cheap flash serial memories.  I'm using their 1 Mbit serial flash to config
a Spartan 2E chip.  I had to make my own device programmer - basically
a single CMOS chip used as a level translator and a page of C code to
write/read it through a PC parallel port.  And, I had to make up a minimal
circuit to send a read from address zero command into the chip.  That takes
two SSOP  packages on the board next to the FPGA.  These chips can handle
up to 25 MHz in their ordinary mode, and up to 32 MHz if you tolerate a
one byte delay before output.  Nice that Xilinx will waif for a byte of FF
before starting to interpret the config bitstream.

I think the 1 MBit chip is about $1.50 in small quantities, I get them 
from Mouser.
They have larger, I don't remember how big they go.

Jon