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Old 05-11-2006, 08:04 AM
Mark McDougall
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Default XCFxxP Plaform Flash Device Questions

Hi,

Was wondering if anyone has used the XCFxxP devices with revision
selection controlled via the internal REVSEL bits rather than the
external REVSEL pins?

I'm assuming the REVSEL bits are, once programmed, persistent
(non-volatile), yes? Is it possible to re-write the REVSEL bits without
having to download a new bitstream as well?

Finally, can anyone see a problem with the FPGA bit-bashing the JTAG on
the PROMs to re-program both bitstreams and REVSEL bit settings? And
what about the FPGA sending the CONFIG command to the PROM to initiate a
re-configuration of itself?

TIA
Regards,

--
Mark McDougall, Engineer
Virtual Logic Pty Ltd, <http://www.vl.com.au>
21-25 King St, Rockdale, 2216
Ph: +612-9599-3255 Fax: +612-9599-3266
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Old 05-11-2006, 08:12 AM
Alan Nishioka
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Default Re: XCFxxP Plaform Flash Device Questions

Mark McDougall wrote:
> Finally, can anyone see a problem with the FPGA bit-bashing the JTAG on
> the PROMs to re-program both bitstreams and REVSEL bit settings? And
> what about the FPGA sending the CONFIG command to the PROM to initiate a
> re-configuration of itself?


I haven't used any of the revsel features, so I can't answer that part,
but I have used the config command to re-config an fpga (where I forgot
to connect the prog line) and it works just fine.

But I think it would be better to use the prog line to initiate
re-config.

Alan Nishioka

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  #3 (permalink)  
Old 05-11-2006, 08:19 AM
Mark McDougall
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Default Re: XCFxxP Plaform Flash Device Questions

Alan Nishioka wrote:

> I haven't used any of the revsel features, so I can't answer that
> part, but I have used the config command to re-config an fpga (where
> I forgot to connect the prog line) and it works just fine.


CONFIG was sent from/via the FPGA itself?

> But I think it would be better to use the prog line to initiate
> re-config.


Momentarily forgot about that option - thanks!

Regards,

--
Mark McDougall, Engineer
Virtual Logic Pty Ltd, <http://www.vl.com.au>
21-25 King St, Rockdale, 2216
Ph: +612-9599-3255 Fax: +612-9599-3266
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  #4 (permalink)  
Old 05-11-2006, 08:36 AM
Antti
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Default Re: XCFxxP Plaform Flash Device Questions

Where did you read that REVSEL are non-volatile??

To my knowledge the XCFxxP can not be used to implement safe multiboot
triggered by the FPGA without using external non-volatile logic kludge
- Xilinx has some appnotes using coolrunner to control the REVSEL and
reboot

Antti

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Old 05-11-2006, 02:09 PM
Alan Nishioka
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Default Re: XCFxxP Plaform Flash Device Questions

Mark McDougall wrote:
> Alan Nishioka wrote:
>
> > I haven't used any of the revsel features, so I can't answer that
> > part, but I have used the config command to re-config an fpga (where
> > I forgot to connect the prog line) and it works just fine.

>
> CONFIG was sent from/via the FPGA itself?


Yes. I always connect the jtag lines back to io lines for true field
programability. Usually, I rely on power cycling to reload the
configuration. But this app required reconfig without user
intervention. So I wrote a little state machine to send the jtag
config command to the prom.

I also considered sending the jtag sequence to the fpga to toggle the
prog pin, but I figured config was easier.

But in my next design, I am going to connect the prog pin to an io
line.

Alan Nishioka

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