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Message
From: "Daniel Quintero" <danielqg@i...>
Date: Fri, 31 Oct 2003 20:42:02 +0100
Subject: Re: [oc] Problems with AX8 and Xilinx XST
Hi Antti
> I cant recall what exactly I did but, well some test code works
> in the FPGA, pretty much all works in simulator, but in the real
> FPGA design code does execute correctly, I used Chipscope connected
> to the AVR core and looked at instruction trace, depending what
> instruction follow some code is not executed incorrectly.
>
> I looked at the VHDL and found that the RTL code can not be correct.
> dont recall details, but I wasnt able to make a quick fix :(
>
> did you run your code in the FPGA or simulator?
With the core syntitized on Synplify, the code runs perfecly both on
post-syntesis simulation as in the fpga hardware. Even with large C programs
i can't detect any problem.
But when i sintetize it using XST, it's fails even with the most simple
program, not only in FPGA hardware, but also in post-syntesis simulation,
even after of any mapping or p&r. The most annoing thing is not that fails
on both, is that the wrong results are exactly the same.
For example, i maded a very simple program that outputs sequencial numbers
to portd. Using XST i get the wrong output of 00h, 80h, 81h, 41h, 42h, C2h,
C3h, 23h, 24h, A4h, A5h... and so. this output is exacly the same on
post-syntesis simulation as in the FPGA hardware. Also changing syntesis
paramers and memory styles, i get exacly this sequence. Using Synplify i get
a perfect sequence of numbers: 0, 1, 2, 3,.. etc. So i think that the
problem is related to some bug or limitation of XST that makes to fail with
the sintaxis and the coding style of the core.
I will like to find what is exactly the module or the part of the design
that is causing all this. To do this will be necessary write some
testbenches and test the AX8 module by module. I don't have so much time to
do it, but i like to try it. Will be funny discover a unknown bug in XST ;-)
Grettings.
Daniel Quintero Gonzalez
www.itoosoft.com - 3DStudio Plugins
danielqg@i...
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