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JTAG - CLK Pin limited to 0.7V

Ad13
Beginner
489 Views

I have 2 x  custom boards with 10CX085YU484E6G and a MT25QU01GB flash device that have been working fine. However, for some reason Quartus changed the device and when I last programmed the FPGA and Flash with the wrong image I can now no longer see the device on JTAG. It cannot detect anything on the JTAG chain.

I've tried removing the MT25QU010GB device, and when I put a scope on the JTAG clock signal it is clean and square but only gets to at about 0.7V. TDI looks good, but the CLK signal appears clamped.

Could I have damaged the JTAG CLK inputs somehow?

I've done exactly the same thing on both boards with now get identical behaviour.

Any help appreciated.

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8 Replies
NurAiman_M_Intel
Employee
474 Views

Hi,

 

Thank you for contacting Intel community.

 

That might be due to issue with USB Blaster. Kindly follow the workaround in KDB below (it is also applicable for USB Blaster):

https://www.intel.com/content/altera-www/global/en_us/index/support/support-resources/knowledge-base...

 

Thanks.

 

Regards,

Aiman


Ad13
Beginner
466 Views

Hello Aiman,

Thanks for your input.

While the certificate had indeed expired, fixing that issue did not solve my problem. This is verified on 3 different PCs with multiple JTAG cables (USB Blaster 1 and 2).

Interestingly on one setup doing Autodetect does detect a device but with an unknown ID (UNKNOWN_2EF20DD). Screenshot attached.

I have also noticed with USB Blaster 1 the clock gets to about 400mV, and on USB Blaster 2 the clock is about 0.7V.

Many thanks.

Adrian.

 

NurAiman_M_Intel
Employee
457 Views

Hi Adrian,


Can you try the solution in the KDB below? As the error shown that the TCK and TMS might have a problem. Also, please check the connection of the TDI and TDO.

https://www.intel.com/content/www/us/en/programmable/support/support-resources/knowledge-base/soluti...


Regards,

Aiman


Ad13
Beginner
454 Views

Hello Aiman,

 

Thanks for your response.

 

I have verified multiple times the pull-up and pull-down resistors on the JTAG lines.

The TCK signal is clean, crisp and not in any way noisy - but just clipped at 0.7Volts. TCK is pulled low through a 1K resistor.

I've tested with 4 cables - a mix of Altera USB Blaster 2, 1 and 3rd party tools. The actual level of the TCK signal changes depending on the cable used, with USB Blaster 2 being the best.

Pin 4 is at 1.8V, which is the VCCIO level and VCCPGM level.

All rails are as expected - the device exits reset as it is configured for active serial (via MSEL) and I can see it try and load an image from the flash device.

 

As a test I added a 10K pull up resistor to TCK with no download cable attached, and similarly it only goes to 0.7V.

Must be a damaged input? How can I have done this by programming with the wrong image? It really was immediate, on 2 boards, after programming with the wrong device selected. Could it have sent one of the reserved JTAG codes?

Many thanks,

Adrian

NurAiman_M_Intel
Employee
409 Views

Hi Adrian,


Apologize that previous answer did not solve your issue.


  • Since you mention that it work previously, is the design compiling in new Quartus? or any change when compiling the design?
  • Where did you measure the JTAG clock? is it the 10 pin header on board or the output from USB Blaster?


Regards,

Aiman




NurAiman_M_Intel
Employee
378 Views

Hi,


Any update for this request? I believe a request has been open in Intel Premier Support. Kindly response to the support.


Thanks.


Regards,

Aiman


Ad13
Beginner
374 Views

Dear Aiman,

 

Sorry for the delay.

I can compile and download the design to the one remaining board without issue, and have done so many times.

I am measuring TCK actually on the PCB - PIN1 of the 10 pin header.

The actual voltage does depend on the type of USB Blaster used - USB Blaster 2 gets to about 0.7V but others are slightly lower.

 

Many thanks,

Adrian  

NurAiman_M_Intel
Employee
353 Views

I’m glad that your question has been addressed, I now transition this thread to community support. If you have a new question, feel free to open a new thread to get the support from Intel experts. Otherwise, the community users will continue to help you on this thread. Thank you.


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