UNKNOWN BYPASS problem

hamidkavianathar · Sep 28, 2019

hey guys
I have designed a custom board with a fpga. when I do initialize chain in iMPACT I recevice this message:

Attempting to identify devices in the boundary-scan chain configuration...
INFO:iMPACT - Current time: 9/28/2019 5:34:02 PM
PROGRESS_START - Starting Operation.
Identifying chain contents...INFO:iMPACT:1588 - '0':The part does not appear to be Xilinx Part.
'0': : Manufacturer's ID =Unknown , Version : 15
INFO:iMPACT:501 - '1': Added Device UNKNOWN successfully.
----------------------------------------------------------------------
----------------------------------------------------------------------
done.
PROGRESS_END - End Operation.
Elapsed time = 0 sec.

I have measured the voltage of all vcc pins. they are correct. but some IO pins have strange values. for example the voltage of them is 1.5 v.
here is my schematic:

could you please tell what is wrong with my board?
thanks in advance.

barry · Sep 28, 2019

1) A schematic with no resistor values is kind of useless. It’s also incomplete. Where do the JTAG signals go?
2) Have you looked at signals with a scope while initializing?
3) Unconfigured IO is floating; what voltage did you expect?
4) Try slowing down the clock speed and see if that helps.
5) These types of problems are often related to Pcb layout.

hamidkavianathar · Sep 29, 2019

thanks berry for attention. you are right. this is my schematic:

I have checked the jtag signals on FPGA pins. they are electrically connected. I expect the IO pins be 0 or 3.3 volt. at least they should not change. but I have an led on board that some times is off and some times is on. I also slowed down the clock speed but it did not change.

KlausST · Sep 29, 2019

Hi,

Please confirm with a scope that all power supplies are stable during programming.

Klaus

hamidkavianathar · Sep 29, 2019

Hi KlausST
thanks for the reply. I have checked it multiple times. I have measured them when I initialize the chain. they are constantly 3.3 and 1.2 volt.
I have used a very high quality PMIC in my board.

FvM · Sep 29, 2019

I have checked the jtag signals on FPGA pins. they are electrically connected.

Did you check if TDO is activated at all and echoes TDI during chain identification or stays in tri-state?

hamidkavianathar · Sep 29, 2019

yes I have checked it. I have taken photo of them.
TDI:

TDO:

TCK:

TMS:

FvM · Sep 29, 2019

Perhaps a member familiar with Xilinx can check if this looks like useful JTAG chain identification sequence. To me, it doesn't.

I would expect a sequence resetting the TAP controller and reading the ID register, which involves more TMS and TCK transitions, see e.g. https://www.edaboard.com/showthread...RA-Max-7000A&p=1658491&viewfull=1#post1658491

hamidkavianathar · Sep 29, 2019

I have a development board with the same FPGA that works properly. when I do "initialize chain" in my development board and my custom board, I see the exactly the same signals.

ads-ee · Sep 29, 2019

hamidkavianathar said:
I have measured the voltage of all vcc pins. they are correct. but some IO pins have strange values. for example the voltage of them is 1.5 v.
here is my schematic:

Which pin(s) show 1.5V?

FYI TDI of the Xilinx USB platform cable is an output of the pod and and input for the FPGA, TDO is an input to the Xilinx USB platform cable and an output of the FPGA. If you switch them TDO(cable)-TDI(fpga) and TDI(cable)-TDO(fpga) then I would expect to see 1.5V when they are in contention.

hamidkavianathar · Sep 30, 2019

ads-ee said:
hamidkavianathar said:

I have measured the voltage of all vcc pins. they are correct. but some IO pins have strange values. for example the voltage of them is 1.5 v.
here is my schematic:

Which pin(s) show 1.5V?

FYI TDI of the Xilinx USB platform cable is an output of the pod and and input for the FPGA, TDO is an input to the Xilinx USB platform cable and an output of the FPGA. If you switch them TDO(cable)-TDI(fpga) and TDI(cable)-TDO(fpga) then I would expect to see 1.5V when they are in contention.

Click to expand...

thanks for comment. I have used a 4.7 k ohm resistor for pulling up HSWAPEN pin. now I changed it with a 330 ohm resistor and all of them are 0 volt.

- - - Updated - - -

in ug380 it is written that:

If JTAG is the only configuration mode, then PROGRAM_B, INIT_B, and DONE can be
tied High to a 330Ω resistor.

Click to expand...

I also tried this configuration. but I still receiving the same message.

UNKNOWN BYPASS problem

hamidkavianathar

Member level 5

barry

Advanced Member level 7

hamidkavianathar

hamidkavianathar

Member level 5

KlausST

Advanced Member level 7

hamidkavianathar

hamidkavianathar

Member level 5

FvM

Super Moderator

hamidkavianathar

hamidkavianathar

Member level 5

FvM

Super Moderator

hamidkavianathar

hamidkavianathar

Member level 5

ads-ee

Super Moderator

hamidkavianathar

Member level 5

Similar threads

UNKNOWN BYPASS problem

Member level 5

Advanced Member level 7

Member level 5

Advanced Member level 7

Member level 5

Super Moderator

Member level 5

Super Moderator

Member level 5

Super Moderator

Member level 5

Similar threads

Privacy & Transparency

Privacy & Transparency