iMX6 Dual Boot Failure

[giacomobiancala]

We have some problems on a custom board equipped with iMX6 Dual (IMX6D7CVT08AD).

The boards provides 1GB NAND FLASH (MT29F8G08ABACAH4:C).

The boards provides 1GB DDR3 DRAM (4 x H5TC2G63GFR-PBA).
We produced 300 boards. 

About 75% of them have no problem and they boot correctly every power on / HW reset.

25% of them have some problems during the boot procedure. They fail booting one time on 20/30 power on. 

It happen both by switch on the power of the board than by pushing reset button. Cause of it I think it is not a problem about voltage sequences at power on.

The problem is the same both from NAND Flash than SD CARD boot device. So the problem is not of the specific device.

We have BOOT_MODE0=0 and BOOT_MODE1=1 (internal Boot). 

If we set boot mode as Serial Downloader, USB OTG has been always recognized by a PC so it seems a problem of some BOOT GPIO.

We have following GPIO configurations at booting:

- BOOT_CFG1 [7:0]   11000000   (NAND FLASH)   01000000   (SD) 

- BOOT_CFG2 [7:0]   00000000     

- BOOT_CFG3 [7:0]   not connected (floating)

- BOOT_CFG4 [7:0]  not connected (floating)

Could be a problem about floating BOOT gPIO?

At the moment we are using an external Watchdog HW in order to solve the problem but we would understand the cause of boot failure.

Thanks

[giacomobiancala]

Thank You for quick replay.

Today I have performed some tests.

I have verified when reset signal goes high both power supplies than 32KHz oscillator are stable.

Moreover I think the problem is not about power sequences because if I just push HW reset of processor the boot failure could happen again. In this case all the power supplies are stable. 

Also ERR7926 seems not related to my problem because when reset signal is deasserted 32Khz clock is always present.

Tomorrow I will check something about ERR009678.

Thank You,

Giacomo

[Yuri]

Hello,

   You may create request  \ ticket in order to review the schematic.

https://www.nxp.com/support/support:SUPPORTHOME?tid=sbmenu

Regards,

Yuri.

[Yuri]

Hello,

   Please look at ERR007926 erratum description in the Errata (ROM: 32 kHz internal oscillator timing inaccuracy may affect
SD/MMC, NAND, and OneNAND boot [i.MX 6Dual/6Quad Only])

https://www.nxp.com/docs/en/errata/IMX6DQCE.pdf 

  Also, erratum ERR009678 (ROM: SD/EMMC/NAND prematurely times out during boot [i.MX
6Dual/6Quad Only]) may be interesting.

  Additonally, according power up sequence requirements in the Datasheet:

   POR_B signal controls the processor POR and must be immediately asserted at
power-up and remain asserted until the VDD_ARM_CAP, VDD_SOC_CAP, and VDD_PU_CAP
supplies are stable.

https://www.nxp.com/docs/en/data-sheet/IMX6DQCEC.pdf 

   So, please check Your design regarding the mentioned above comments.

Have a great day,
Yuri

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