BAT_FAIL bit is always 0(Wakeup from LPOFF)

[vaibhav_sharma]

BAT_FAIL bit in INIT_VREG register is always 0(Even on reset), which shows that the POR never occurred. I am using debug mode. The RSTB_EXT bit in DIAG_SF_IOs register is 1 every time, I run the code.

Q1. Why is the BAT_FAIL bit always 0(No POR)? Even after restarting the power supply.

Q2. Why is this bit (RSTB_EXT) always 1? Does this represent the POR as well or just the external reset cases? Everytime the board starts, this bit is set. Does restart of power supply to SBC comes under reset category?

What can be the possibility of that behaviour of both the bits. Please let me know.

Thanks in advance.

[reyes]

Hi,

Please make sure VSUP on FS65 is 0V before re-enable power supply for FS65. 

Sometimes FS65 register is not reset due to residual voltage on capacitor of Vsup, so the BAT_FAIL is 0. 

Can you use an oscilloscope to monitor RSTB of FS65 pin during normal powering up to make sure there are no Reset happen?

Have a great day,
Jose

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[vaibhav_sharma]

Hi Reyes,

Thanks for the response.

In non-debug mode, the BAT_FAIL bit becomes 1 whenever the power supply is getting restarted. But if I want to check it on debugger by entering into debug mode & restarting it again, it shows the same behavior(NO POR). Is it because of any reset occurring while using SBC in debug mode? If so, which bit can be significant other than RSTB_EXT to know the exact cause of reset?

[reyes]

Hi Vaibhav,

BAT_FAIL bit will be cleared once it is read by SPI command.  That means if MCU read it twice, MCU can only get '0' in second reading.  RSTB_EXT have same behavior that Read can reset it.  

There are no dedicated bit to indicate reset reason, but you can check some diagnostic register to know the reset reason: 

DIAG_VPRE

DIAG_VCORE

DIAG_VCCA

DIAG_VAUX

DIAG_VSUP_VCAN

DIAG_CAN_FD

DIAG_CAN_LIN

DIAG_SPI

DIAG_SF_IOS

DIAG_SF_ERR

Regards,

Jose

NXP Semiconductors