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Observer
Observer
7,990 Views
Registered: ‎07-25-2016

KC705 JTAG chain and FMC HPC connector

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When I connect a 3rd party board (TI ADC12D1600RFRB) to the FMC HPC connector, I loose connection with the JTAG chain and I am unable to program the FPGA. According to me, it is the JTAG bypass switch which is opened by HPC pin H2, which is connected to ground on the daughter board. The JTAG pins on the HPC connector (D29-D31) of the daughter board are not connected, neither bypassed.

 

Is there a way to bypass this JTAG switch (U76) manually on the KC705?

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Adventurer
Adventurer
7,970 Views
Registered: ‎02-24-2012

@geerard

 

Hi,

 

dirty hack is to short pins 1 and 2 of the U76.

 

Best Regards,

 

Stephan

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Adventurer
Adventurer
7,971 Views
Registered: ‎02-24-2012

@geerard

 

Hi,

 

dirty hack is to short pins 1 and 2 of the U76.

 

Best Regards,

 

Stephan

View solution in original post

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Observer
Observer
7,964 Views
Registered: ‎07-25-2016

In the mean time, I've also found a topic on the TI E2E forum describing this issue on a similar board, confirming your proposal.

https://e2e.ti.com/support/data_converters/high_speed_data_converters/f/68/p/394209/1393474

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Moderator
Moderator
7,957 Views
Registered: ‎07-23-2015

@geerard Or one way would be to pull R9.1 pin to Ground. Whichever works for you. 

 

Btw is U76 broken on your KC705?

 

Is it still under warranty? If not, then the above suggested methods would be the only hack which you would need to revert back when you remove the FMC daughter card. 

- Giri
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Observer
Observer
7,951 Views
Registered: ‎07-25-2016

@gnarahar,

 

The U76 is not broken, and pulling R9.1 pin to ground would permanently open the JTAG chain, regardless of whether or not an FMC board is connected. This is thus not an option. Shorting this R9 is also not an option, since the pin on the ADC board is direcly connected to the ground plane, which would create very large currents.

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Moderator
Moderator
7,948 Views
Registered: ‎07-23-2015

@geerard My bad. I missed the point in your original post about JTAG pins on the FMC daughter card not being connected. 

 

Yeah, R9.1 doesn't help. Shorting Pins 1 & 2 of U76 is the only way to go. 

- Giri
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There's no such thing as a stupid question. Feel free to ask but do a quick search to make sure it ain't already answered.
Keep conversing, give Kudos and Accept Solution when you get one.
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Xilinx Employee
Xilinx Employee
7,765 Views
Registered: ‎08-01-2012

As it mentioned in previous post TDI and TDO short is one option.

 

Before that please check the JTAG chain connections carefully. Especially TDO-TDI-TDO-TDI loop,  There could be some extra loops for JTAG connections. Also make sure TCK and TMS connected to all devices including third party device.

 

Is third party device is as per JTAG IEE1149.1 standard? 

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Adventurer
Adventurer
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Registered: ‎12-04-2019

Hello Giri

 

How do you short it? Do you have any jumpers in the board? Or is there any other way?

 

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Observer
Observer
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Registered: ‎07-25-2016

This is an error on the daughterboard and could not be foreseen by Xilinx. Therefore, no jumpers were included on the KC705 and manual soldering is required.

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Adventurer
Adventurer
558 Views
Registered: ‎12-04-2019

Thank you very much. I guess shorting both U76 and U77 will be required as I will be using both HPC and LPC connectors.

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Observer
Observer
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Registered: ‎07-25-2016

Keep in mind that these shorts are only needed if the daughterboard does not have the JTAG pins linked through, which was the case with the board I was using. If you take a daughterboard that is VITA 57.1 compliant or where the JTAG pins (TDI and TDO) are connected, this manual patch would not be needed. Furthermore, I believe the daughterboard I was using was incompatible with the LPC connector, if I'm correct.

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Adventurer
Adventurer
533 Views
Registered: ‎12-04-2019

Hello @geerard 

 

I am using a KC705 board and the FMC Connector cables I am using are VITA 57.1 compliant too. But I loose the JTAG programmability when I connect the cables. I am also clueless which pins in the Switch to short. I has two one one side and 3 pins to the other as given below. My guess I am supposed to the two on the right side to close the switch as marked yellow in the picture. Am I right? 

 
 

ss.JPG

 

Also it says so in the KC705 documentation.

 

ds.JPG

 

 

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Adventurer
Adventurer
525 Views
Registered: ‎12-04-2019

Sorry my bad. I got to know to which of the pins to short.

ss.JPG

 

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513 Views
Registered: ‎01-22-2015

@naarayananrao 

To regain JTAG operation, you can modify the FMC daughter board instead of modifying the KC705.

For example, if you are using the XM105 daughter board, you can short two pins on the XM105 as described in the following AR.

https://www.xilinx.com/support/answers/52888.html

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Adventurer
Adventurer
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Registered: ‎12-04-2019

Thank you professor.

I am looking into using alternative methods for programming the FPGA using Linear or Quad SPI flash as currently I don't have an access to a solder.

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