08-19-2016 02:03 AM
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?
08-19-2016 03:16 AM
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.
08-19-2016 04:00 AM
@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.
08-19-2016 04:39 AM
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.
08-19-2016 05:16 AM
@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.
08-30-2016 08:26 AM
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?