Boundary Scan chain fails 150ms after EXTEST instruction

[goepel]

Hello,

I am having trouble in Boundary Scan testing an iMX6UL device, exact number is IMX6G2CVM05AA, revision is 1.1.

When entering EXTEST mode, the scan chain breakes after about 150ms. That is enoutgh for testing the scan chain itself but not for the interconnection test and cluster tests. The iMX6 device delivers 0x0000 at its TDO pin afterwards.

It looks like a TAPRESET (TRST or entering the state) can revers the result, I suspect an internal reset.

I need to know how to make sure the device is not executing any reset after entering EXTEST instruction.

I also tried:

- loading instruction "ENABLE_EXTRADEBUG" and entering different values to address 4 and address 7 registers but without success.

I am looking forward to your soon reply Please don't hesitate to ask in case of further questions.

With best regards

Jan Heiber

[art]

What is the logic state of the JTAG_MOD pin when you are trying to perform the boundary scan test? You have to have this pin High to be able to perform the boundary scan test. Otherwise, the scan chain is connected to the ARM core debug cell.

Also, please refer to the Chapter 7 of the i.MX6UL Hardware Development Guide document, available on the processor's Documentation web page (check the "User Guides" section):

http://www.nxp.com/products/automotive-products/microcontrollers-and-processors/arm-mcus-and-mpus/i....

Have a great day,
Artur

[goepel · Accepted solution]

Hello,

the reason for this behaviour was a low-pulse generated on the SNVS_PMIC_ON_REQ pin towards the PMMU device which executed then the reset. This happened when entering EXTEST since there was no pull resistor between iMX6UL and PMMU.

Best regards

Jan