TMS470MF06607: CCS Code Composer Studio error: unable to access device register

Hi Laurent,

  - Can you check your board for proper soldering and flux for a strong bond. Can you clean the JTAG pins?

  - In CCS, you can do a JTAG scan chain test for the XDS200. What is the result?

  - Do you still see any pins toggling per your application firmware loaded to the suspected MCU? Or there are no longer activities on the MCU. 

  - Do you still have proper power supply to the malfunctioned circuit?

  - Do you have clock to the malfunctioned circuit?

  - Can you do a ABA swap between the two MCUs on the board? Will the suspected MCU continue to fail after moved to the good side? Will the good MCU continue to work after moved to the suspected side?

The A-B-A Swap Method is a simple cross check test, which can confirm the observed issue is not systemic.

• A-B-A Swap Method
  (1) Remove the suspected component (A) from the original failing board.
  (2) Replace the suspected component (A) with a known good component (B) and check if the original board now works properly.
  (3) Mount the suspected component (A) to a known good board and see if the same failure occurs on the good board.

Step 3 is important because it helps us to exclude any possibility that the issue is caused by a systemic issue or the interaction of multiple slightly bad components on a good board.

Hi Charles,

Thanks for reaching out, please see in order, replies to your questions.

- The PCB have been soldered and inspected to IPC standard, JTAG pins / connectors headers are clean on both circuits.

- Unfortunately, we didn’t do this specific test at the time with CCS and the MCU has now been swapped for a working one. But we established that the JTAG chain was working earlier on both circuits and by programming the other circuit when the fault manifested. We also tried to program the faulty MCU with Uniflash but it also failed to connect.

- There was no activity on the faulty MCU, no code was running.

- Yes, both circuits are powered with the same power supply, all working fine.

- Yes clock was present.

- The faulty MCU was removed and swapped with a 3^rd working MCU, code loaded with the same JTAG setup. The faulty MCU is now in quarantine, we wanted to avoid tampering with the MCU.

Is there a tool different than CCS or Uniflash that is available to us / TI to test this faulty MCU? It is important that we understand fully the failure mechanism.

Many thanks,

Laurent

Hi Laurent,

   I think it is a MCU problem but I don't know what caused the MCU to die.

  - For how long have you been using the malfunctioned MCU successfully before the problem occurred? 

  - Can you do a resistance check on the pins? Is the device shorted?

  - Do you recall a EOS (Electrical Overstress) event that might have happened (e.g. ESD, high current, high voltage) while you were trying to program the device?

  At the moment I tend to think the MCU failed due to an EOS event. 

Hi Charles,

Sorry for my late reply, I wanted to reply earlier but then the TI forum was down for maintenance.

In answers to your questions:

-The device had undergone several re-programming (in the 10s, not 100s)
-Comparing impedances with an identical circuit using a multimeter, NO differences in JTAG impedances to GND or 3V3 were detected.
-No, no EOS noted.

Please note our test benches / test areas are following best practice in terms of ESD management and the MCU had been programmed successfully just prior to this so no changes in the set up had been done.

Is there a way to have further support from TI in terms of a technical investigation of the MCU? What would you suggest next?

Thanks,
Laurent