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Visitor brianlojeck
Visitor
2,262 Views
Registered: ‎10-02-2017

Trouble using Chipscope on multi-chip JTAG chain

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I'm no chipscope expert, but from my reading of the 226 page user manual, it's smart enough to work on a board that has a long JTAG chain.

 

I'm working with a PWA that contains a multi-chip JTAG chain. The chain works, as the product's "self test" uses it to run some basic boundary scan and the like.

 

The VCC signal is seen correctly by the Platform Cable (the light turns green).

 

However, when I try to connect with chipscope, I get error:

ERROR: No devices detected while scanning the JTAG chain
ERROR: Failed detecting JTAG device chain
ERROR: Opened Xilinx Platform USB Cable but failed to detect JTAG Chain.

 

I'm using Chipscope 14.7 and the Xilinx Platform Cable USB II.

The on-board JTAG controller is tri-stated, so there should be no conflict on the JTAG chain for control.

The other chips on the PWA are all standard commercial parts that otherwise work well with JTAG.

 

I do notice, the JTAG chain on the PWA does not use the HALT line. Just TDO, TMS, TCK, TDI, VREF, GND.

 

Is there any hope for me to be able to debug this design?

 

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1 Solution

Accepted Solutions
Explorer
Explorer
3,204 Views
Registered: ‎01-09-2012

Re: Trouble using Chipscope on multi-chip JTAG chain

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I had as well such problems when using very slow devices or suboptimal PCB layouts... Can you try following:

1.) Make sure all JTAG devices are powered.

2.) Change speed to 750Kbit/s

3.) If nothing of the above helped check with a scope the signal levels and shape.

 

Cheers

Goran

 

View solution in original post

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10 Replies
Scholar markcurry
Scholar
2,253 Views
Registered: ‎09-16-2009

Re: Trouble using Chipscope on multi-chip JTAG chain

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Forget chipscope for the moment - does impact work? 

 

We've daisy chain devices on our board - but usually only a few deep.  Just thinking off the cuff here but I know one board has 2 Virtex6 devices, 1 Virtex5, and another (non-Xilinx) device.

 

Works fine with both impact and chipscope.  As it should, as that how JTAG is supposed to work.

 

I'm wondering, however in what your definition of "long" means....Perhaps there's some (perhaps artificial) limit within the Xilinx tools?

 

Regards,

 

Mark

 

 

 

 

Visitor brianlojeck
Visitor
2,241 Views
Registered: ‎10-02-2017

Re: Trouble using Chipscope on multi-chip JTAG chain

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iMPACT also has connection problems.

 

I don't know the exact number of devices, but it's less than 10. I'd have to dig into the schematics to add it all up.

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Moderator
Moderator
2,210 Views
Registered: ‎02-09-2017

Re: Trouble using Chipscope on multi-chip JTAG chain

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Hi @brianlojeck,

 

What is the version of ChipScope you are using? 

 

Just for the sake of debugging, is it possible to try with less devices in the JTAG chain (maybe just one) and see if it works?

 

That way we can have a better idea if the issue is with the cable drivers or with the ChipScope not handling well the multiple devices in the chain.

Andre Guerrero

Product Applications Engineer

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Visitor brianlojeck
Visitor
2,203 Views
Registered: ‎10-02-2017

Re: Trouble using Chipscope on multi-chip JTAG chain

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Version 14.7.

 

Unfortunately, it's not possible to change the jtag chain. This is a completed production board.

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Explorer
Explorer
3,205 Views
Registered: ‎01-09-2012

Re: Trouble using Chipscope on multi-chip JTAG chain

Jump to solution

I had as well such problems when using very slow devices or suboptimal PCB layouts... Can you try following:

1.) Make sure all JTAG devices are powered.

2.) Change speed to 750Kbit/s

3.) If nothing of the above helped check with a scope the signal levels and shape.

 

Cheers

Goran

 

View solution in original post

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Visitor brianlojeck
Visitor
2,164 Views
Registered: ‎10-02-2017

Re: Trouble using Chipscope on multi-chip JTAG chain

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I've accepted the above post as a solution because it's good advice, but the problem, in this case, was the Id10T unit (ie: me).

 

Pure user error. Sorry for the trouble.

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Scholar markcurry
Scholar
2,161 Views
Registered: ‎09-16-2009

Re: Trouble using Chipscope on multi-chip JTAG chain

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"Id10T" is lost on me (but I'm really bad at those sorts of puzzles).  My favorite term for this type of mistake: "Error between keyboard and chair".

 

Good that you found it.

 

Regards,

 

Mark

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Explorer
Explorer
2,152 Views
Registered: ‎01-09-2012

Re: Trouble using Chipscope on multi-chip JTAG chain

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@brianlojeck

 

No worries, this weird feeling after finding the mistake is something called experience and happens to everyone working hard.

 

Cheers

Goran

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Visitor brianlojeck
Visitor
2,147 Views
Registered: ‎10-02-2017

Re: Trouble using Chipscope on multi-chip JTAG chain

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@markcurry wrote:

"Id10T" is lost on me (but I'm really bad at those sorts of puzzles).  My favorite term for this type of mistake: "Error between keyboard and chair".

Mark


 "idiot". :-)

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Scholar markcurry
Scholar
1,150 Views
Registered: ‎09-16-2009

Re: Trouble using Chipscope on multi-chip JTAG chain

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Hah!  And I missed that.. Looks like that label is appropriate for more than one reason!

 

Regards,

 

Mark

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