iMX537 efuse issues

[chiranjeevimata]

Hi All,

We are facing a serious issues with the boot settings. We have 4 target boards which are configured to boot from SD Card with Boot_Mode[1:0] = 0. We are seeing that in 2 boards are booting from SD Card when powered on. In remaining 2 boards we are seeing that it was not booting. When we started debugging we accidentally found that when ever we are pulling BOOT_MODE[1] to high the device started booting from SD Card. Also we observed that if we pull BOOT_MODE[1] during power on it doesnt boot only when the power is on and stable if we pull high it starts booting. We are not able to understand the problem. Please help us in finding the root cause of the problem if any one of you have faced or come across this type of issue. This issue is stopping us from moving forward with the production.

Regards,

Chiranjeevi M

[igorpadykov]

Hi Chiranjeevi

you can check what boot mode uses processor

reading with jtag SRC_SBMR register.

Also what do you mean by "Boot_Mode[1:0] = 0"  ?

Both zeros ? In such case (BOOT_MODE[1:0] = 0b00)

please check fuse that BT_FUSE_SEL = 1.

If BT_FUSE_SEL = 1, all boot options are controlled by the eFUSEs

described in Table 7-2 IMX53RM .

Also boot pins should be stable during power-up.

Best regards

igor

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[chiranjeevimata]

Hi Igor,

Boot_Mode[1:0] = 0; means BOOT_MODE[1:0] = 0b00. So we are booting as per the bit settings done on the GPIO's in Table 7-3 of IMX53RM.  The Boot pins are stable at booting. We are not able to figure out what is that which is causing this peculiar behavior of iMX537. These two boards were initially working fine with BOOT_MODE[1:0] = 0b00. But suddenly stopped booting. During debugging we found this behavior. We are assuming that the efuses have been blown off and hence iMX537 is trying to boot from efuse instead of GPIO. Please let us know if there is any chances that efuses can blow off.

Regards,

Chiranjeevi M

[igorpadykov]

Hi Chiranjeevi

please check fuse BT_FUSE_SEL = 1

probably on these two boards some fuses become blown.

Also check pad VDD_FUSE  - it should not be powered with 3V.

Best regards

igor

[chiranjeevimata]

Hi Igor,

Thanks for your suggestion. We will read the BT_FUSE_SEL bit through JTAG.

And coming to the VDD_FUSE supply, Our design is as per the Eval board schematics where we are using DA9053 PMIC for powering the iMX537.

Mean while could you please let me know what are the possibilities that the Fuses get blown if not done intentionally. And is there any way that can be reversed.

In couple of days we have seen that sometimes these two boards boot even with BOOT_MODE[1:0] = 0b00 , in this case sometimes the booting gets delayed (we have seen that booting happens after 20mins). But after few power cycle we need to set BOOT_MODE[1:0] = 0b01. We are not sure why this behavior is found in only couple of boards and not seen in other boards.

Regards,

Chiru M

[igorpadykov]

Hi Chiranjeevi

fuses may be not-intentionally blown due to incorrect

power-up sequence, for that reason recommended

not to power with 3V pad VDD_FUSE.

Regarding delayed boot, I am inclined to think that this may be

poor soldering issue. Siggest to resolder processor just for test.

Best regards

igor

[chiranjeevimata]

Hi Igor,

I read the BT_FUSE_SEL bit from JTAG and found that it was 0. So it means the efuses are not blown. Is my understanding is correct.

I found that the voltage to NVCC_CKIH is at 2.7V in the non working boards. Also i probed the same voltage in the working boards there i saw the voltage to be 3.0V in one board and 1.8V in other board.

As per Table 6 of iMX53IEC Voltage at NVCC_CKIH should not exceed more than 1.9V. But in few boards which worked for more than 3 months the voltage was 2.7V and in the board which is working from 3months is 3.0V. Could you please provide some insight on the same as why the boards worked for 3months and broke and why the other board is still working even when the voltage on this pin is stressed.

Also if any idea why the board started working when the BOOT_MODE[1:0] = 0b01 only on power up.

Regards,

Chiranjeevi M

[igorpadykov]

Hi Chiranjeevi

operation with power exceeding datasheet may lead to unpredictable

and sometimes weird results, one can work for some time, others not.

Also behaviour as "working when the BOOT_MODE[1:0] = 0b01 only on power up"

may be explained by applying too high voltage to processor.

I would suggest to recheck power-up sequence in  IMX53CEC for "NVCC_CKIH" :

NVCC_CKIH should be powered ON after VCC is stable and before other I/O supplies

(NVCC_xxx) are powered ON.

Best regards

igor