T4240 couldn't be programmed by JTAG

[zhangkun2015]

Hello,

We made a board with reference of T4240RDB, recently we met a problem which is shown in the title. After many checks,

we found an abnormal phenomenon:

1. the impedance between VDD_OVDD_P1V8 and GND is only 9.2 Ohm,while the impedance between P1V8_AVDD and GND is 2262Ohm.
2. 
3. 
4. Is there something wrong with the inner part of T4240?

[ufedor]

The impedance in question is not characterized, so it is not specified what is its normal value.

[zhangkun2015]

ufedor‌             

Hi,I need your help.Thanks a lot.

[ufedor]

Please confirm whether the processor is capable to complete its POR sequence - refer to the T4240 RM, 4.6.1 Power-on reset sequence.

[zhangkun2015]

Thank you for your reply. But Why the impedance between VDD_OVDD_P1V8 and GND is so low？

[ufedor]

Please provide the processor connection schematics as PDF.

[zhangkun2015]

Hi,thank you for your reply.

I am a fresher here. How Can I upload the PDF file ?

[ufedor]

Just attach it to response.

[zhangkun2015]

 Oh, thank you for your remind. 

 I choose the pages of the processor connections  from the schematic,and made them to PDF files.

[ufedor]

Now please describe the processor behaviour and restate the question.

[zhangkun2015]

And the second  abnormal state is :

The 1st foot of JTAG connector is short circuit.

      and the net of  the 1st foot, named "COP_TDO" is directly connected to T4240's pin,which is K42.

Now, we are so worried that there is something wrong with the inside of the T4240.

[zhangkun2015]

OK, the PDF is attached here.

[zhangkun2015]

OK,Let me state the problem from the beginning.

Actually, last week, my board had just been ready for the frist time programme. But the first time we connected the debug device to the board, the problem happened. The figure is shown below.

OK, the Chinese characters could be ignored. So, we began to check the relevant hardware.

Finally,we found two abnormal states.

1.     the impedance between VDD_OVDD_P1V8 and GND is only 9.2 Ohm,while the impedance between P1V8_AVDD and GND is 2262Ohm.  the net of VDD_OVDD_P1V8 is only connected to two places,one is in PDF 24 and the other is in PDF 36