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Spartan 3AN prevent readback ?

I am trying to prevent readback of the bit file from a Spartan 3AN. I am using ise 10.1 (need to keep that for a while to support some older devices). I looked up how to do it in a Xilinx tutorial, but it doesn't seem to work. They say to go into generate programming file/ properties/readback options, and set it for disable readback and reconfiguration. I set this, regenerated the bit file, but after programming the device with Impact, I can still verify the config. I'm assuming if you disable readback, you can no longer verify the device, right?

I also tried all combinations in Impact, which are data protect and data lockdown, these didn't seem to prevent verify, either.

(I did a separate verify AFTER the one done automatically when programming, presumably the read protect would be set after the initial verify.)

Anyone been able to do this and know what I missed?

Thanks,

Jon

Reply to
Jon Elson
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One additional tidbit of info, if you read the bitgen report, it shows Readback as (Not Specified)* so it looks like the GUI system is not passing the disable readback requirement to bitgen.

Do I have to run bitget from the command line? I've never done that before.

Thanks,

Jon

Reply to
Jon Elson

Quite possible.

Worth learning how.

After using it in GUI, there should be a "command log" file (apologies for vagueness, it's been a while since I used 10.x) in the project folder. This will contain the command lines generated by the GUI. You can use these as a starting point and add the flags you need in a text editor.

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documentation/td-p/94148 may be useful. There is a link there to more documentation.

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devref.pdf is the right manual for the wrong ISE version but there ought to be a devref.pdf in the "docs" folder of your installation.

Having started this route, you may find it easy to write a shell script (batch file if you're still using Windows) to repeat a complex series of commands such as rebuilding a stable design.

I still use the GUI for experiments, new designs, until they are reasonably stable, then create a shell script for consistency.

- Brian

Reply to
Brian Drummond

Yes, I've got this in the bitgen report, it is 6 lines long with TONS of switches. Well, I'll try it. But, is it true that bitgen is where the bitfile protection is controlled for the Spartan 3AN with Impact? With CPLDs, it is an option in Impact.

Thanks,

Jon

Reply to
Jon Elson

Are you talking about reading back the bitstream from the FPGA or from the attached SPI flash? I was under the impression that bitgen only controls whether you can read back the bitstream from the FPGA itself. If you use the SPI flash embedded in the Spartan 3AN, then I'm pretty sure anyone can read it back.

-- Gabor

Reply to
Gabor

Assuming this is possible, what I want to do is prevent readback of the internal flash memory of the Spartan 3AN. So, yes, I guess I want to prevent readback from EITHER the live FPGA config OR the flash memory inside the chip.

I thought this was possible, but further reading of Xilinx docs just gets me confused. Well, it is not a critical situation, but I did want to protect my little bit of IP if it just required clicking a button on the GUI or so.

Jon

Reply to
Jon Elson

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