From: Torsten Landschoff on
Hi Eric,

On 28 Feb., 05:38, Eric Smith <e...(a)brouhaha.com> wrote:
> it with the Xilinx cable. You have to use a third party JTAG interface,
> and swap JTAG cables back and forth. :-(
>
> There *must* be some kind of API that Xilinx uses in their own software
> to do this. C'mon, guys, open it up for customer use!

I really wonder why they are keeping it a secret as I don't think that
a JTAG adaptor is so hard to build. Perhaps it was developed by a
third party and Xilinx has no way to open it?

Greetings, Torsten

From: Andreas Ehliar on
On 2007-02-28, Eric Smith <eric(a)brouhaha.com> wrote:
> MotM wrote:
>> Is there a way to access the platform cable USB from a user program
>> (i.e., from outside the Xilinx toolchain) ? What I'd like to do is
>> access a BSCAN module inside my design from a custom win32
>> application.
>
> Andreas Ehliar wrote:
>> Take a look at the following URLs:
>> http://www.xilinx.com/publications/xcellonline/xcell_53/xc_jtag53.htm
>> and http://www.s3group.com/system_ic/gnat/
>
> Those articles show how to acess the JTAG interface from logic inside
> the FPGA. What MotM wants is to access the JTAG chain from the PC.
>
> Unfortunately Xilinx does not provide any API to do this, and believes
> that the interface to their PC4 and Platform USB cables is some kind
> of super-valuable trade secret, so the answer is that you can't do
> it with the Xilinx cable. You have to use a third party JTAG interface,
> and swap JTAG cables back and forth. :-(
>
> There *must* be some kind of API that Xilinx uses in their own software
> to do this. C'mon, guys, open it up for customer use!

If you read the article thoroughly you can see that they include some
TCL scripts that use Xilinx' drivers to access the JTAG interface from
the PC.

I haven't tried this myself but my impression is that you will have
an easier time doing that if you have access to chipscope but it
should be doable without. The following is a paragraph taken from the
first link I posted above:

Software Support
----------------
Xilinx provides all of the tools required for you to write simple scripts
to access the USER registers through the JTAG interface. ISE tools provide
a custom TCL shell (xtclsh), while the Xilinx ChipScope Pro tools provide
a TCL script (Figure 5) (tcljtag.tcl) that creates a number of high-level
TCL commands to control the JTAG interface.



/Andreas
From: Sylvain Munaut on
Andreas Ehliar wrote:
> On 2007-02-28, Eric Smith <eric(a)brouhaha.com> wrote:
>> MotM wrote:
>>> Is there a way to access the platform cable USB from a user program
>>> (i.e., from outside the Xilinx toolchain) ? What I'd like to do is
>>> access a BSCAN module inside my design from a custom win32
>>> application.
>> Andreas Ehliar wrote:
>>> Take a look at the following URLs:
>>> http://www.xilinx.com/publications/xcellonline/xcell_53/xc_jtag53.htm
>>> and http://www.s3group.com/system_ic/gnat/
>> Those articles show how to acess the JTAG interface from logic inside
>> the FPGA. What MotM wants is to access the JTAG chain from the PC.
>>
>> Unfortunately Xilinx does not provide any API to do this, and believes
>> that the interface to their PC4 and Platform USB cables is some kind
>> of super-valuable trade secret, so the answer is that you can't do
>> it with the Xilinx cable. You have to use a third party JTAG interface,
>> and swap JTAG cables back and forth. :-(
>>
>> There *must* be some kind of API that Xilinx uses in their own software
>> to do this. C'mon, guys, open it up for customer use!
>
> If you read the article thoroughly you can see that they include some
> TCL scripts that use Xilinx' drivers to access the JTAG interface from
> the PC.
>
> I haven't tried this myself but my impression is that you will have
> an easier time doing that if you have access to chipscope but it
> should be doable without. The following is a paragraph taken from the
> first link I posted above:

I have tried it and it works.
I use it quite often to put "debug" modules that I can control easly
via my PC without the need for another interface. (And also you don't
have to bring the signals to your top level ;)

It's not very fast though ... IIRC, it takes me almost 30 min to grab
16Mbytes of data ... The wider your User register is, the faster in
my experience.

The interface has changed in 9.1, I haven't tried the new one yet.


Sylvain
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