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  #1 (permalink)  
Old 05-18-2006, 06:24 PM
jvdh
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Default Spartan 3 Readback

I am working on a custom configuration controller that configures a
Spartan 3 through SelectMap and verifies the configuration through
readback.

Configuration is simply writing the .bin file into the S3, no problems
there.

The trouble starts when I want to give the readback commands the the
FPGA - al commands are ignored completely, even though I am using the
same code to write to the device. I'm currently just trying to issue a
SHUTDOWN command to the FPGA, to see if anything happens.

I've checked (and rechecked) that the data appears on the D0-D7 pins of
the FPGA (byte swapped), with CCLK merrily running along, CS_B=0,
RDWR_B=0, and I set persist=yes in bitgen.

The S3 datasheet has an interesting flowdiagram (fig 23, p37) that show
reconfiguration starting with "prog_b low after power on", then "prog_b
high" to avoid clearing the configuration. What is happing there?

Is there anything I'm missing? Some command (on CS_B/RDWR_B perhaps?)
that will make the FPGA aware of my intentions?

Any suggestions will be greatly appreciated.

jvdh

http://www.ee.sun.ac.za/~jvdh

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Old 05-18-2006, 07:18 PM
dand2k
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Default Re: Spartan 3 Readback

Which Spartan3 device are you using? There is an eratta for the
XC3S1500 stating that some of the engineering sample parts have a
readback bug in them. You might want to search the Xilinx support
website for readback failures, or consult the eratta pages for the
device you are using.

Dan

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Old 05-19-2006, 12:29 AM
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Default Re: Spartan 3 Readback

dand2k <[email protected]> wrote:
>Which Spartan3 device are you using? There is an eratta for the
>XC3S1500 stating that some of the engineering sample parts have a
>readback bug in them. You might want to search the Xilinx support
>website for readback failures, or consult the eratta pages for the
>device you are using.


Is there a workaround .. ?

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Old 05-19-2006, 08:02 AM
Eric Smith
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Default Re: Spartan 3 Readback

[email protected]d writes:
> Which Spartan3 device are you using? There is an eratta for the
> XC3S1500 stating that some of the engineering sample parts have a
> readback bug in them.
>
> Is there a workaround .. ?


The workaround is to use production (non-ES) XC3S1500 parts.
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  #5 (permalink)  
Old 05-19-2006, 08:35 AM
Antti
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Default Re: Spartan 3 Readback

hum, lasted time I checke the readback was not available on any S3
production silicon at all due to wafer bug.
has it really been fixed now? If so then its a good thing of course.

Antti

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  #6 (permalink)  
Old 05-19-2006, 10:47 AM
jvdh
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Default Re: Spartan 3 Readback

Dan:

Using a production XC3S200-FT256-4C on a Digilent Spartan 3 starter
kit, nothing funny, hundreds of them must be in use out there... I
haven't found anyone complaining that they can't do readback on them,
but not many people are doing readback on S3s (apart maybe from the
Xilinx Rosetta program)

thanks

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  #7 (permalink)  
Old 05-19-2006, 10:58 AM
jvdh
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Default Re: Spartan 3 Readback

Antti:
That is scary, to say the least...

I found the errata stating that all parts for GQ fabrication process
and date code prior to 0532 do not supprt readback of any nature
(SelectMap and JTAG).

Now I'm just trying to decypher my part number...

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Old 05-19-2006, 11:10 AM
Antti
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Default Re: Spartan 3 Readback

I was scared too, a while ago.
the errata looked like the issue is not going to be fixed at all, but
ASFAIK Xilinx is committed to eventually fix the S3 readback on all
production silicon from the new wafer/fab

antti

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  #9 (permalink)  
Old 05-19-2006, 03:59 PM
jvdh
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Default Re: Spartan 3 Readback

According to the errata, my AFQ device should not be affected - which
makes sense because my JTAG readback is working fine.

I've just realised that I can command the FPGA to shutdown (without
losing configuration, this is one of the first steps of readback) after
I've verified the configuration using JTAG.

So I presume the startup sequence at the end of the JTAG verification
is slightly different from the startup after initial configuration.

Has anyone seen anything similar before? Or knows if the JTAG commands
differ from those in the binary readback file?

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