MCIMX6U5DVM10AC SD card boot start delay

[apines]

Hi,

   We have a design which uses the i.MX6 Dual Lite.  We've built tens of thousands of units without incident so the design is well established.  BOOT_MODE1:0=10 (internal boot mode) and BOOT_CFG1[7:4]=0101 (SD/eSD fast boot).  It boots from an SD Card.  Recently due to procurement issues we switched from MCIMX6U5DVM10AD back to MCIMX6U5DVM10AC, mask set 3N81E.  It still works but now it delays for about 20 seconds before accessing the SD Card.  This was verified by putting a scope on the clock signal of the SD Card and it's clear that it doesn't access the card during that delay.  The type of reset doesn't matter (power on, watchdog, or external), the delay is the present in all cases.  Any insight as to what might be different?  I have some old boards with MCIMX6U5DVM10AC, mask set 2N81E, which do not exhibit this issue.  Also, the date code on the ones which delay indicates they were made in 2020 (code=2023) which seems strange since the MCIMX6U5DVM10AC was supplanted by the MCIMX6U5DVM10AD in 2018.  I'm not sure if that provides any insight.  Thanks in advance for any help.

     -Andrew

[Rita_Wang]

You can see the errata file here https://www.nxp.com.cn/docs/en/errata/IMX6SDLCE.pdf

[apines]

I haven't been able to find anything in the errata that would explain this behavior.  Additionally, we have two CMs building this same board and only one of them is seeing the problem.  Both are using parts marked MCIMX6U5DVM10AC with mask rev. 3N81E but the ones which are exhibiting an additional 20 second delay before booting are marked SNGPR (presumably Singapore) while the ones marked CHINA are functioning normally.  Again, note that not all of the SNGPR parts are showing the delay, maybe about half of them are.

Let me take this opportunity to again berate NXP for changing mask sets without changing part numbers (MCIMX6U5DVM10AC comes with both mask set 2N81E and 3N81E).  Parts distributors don't track parts that way and if some difference between mask sets requires action on the part of the CM or software it's not obvious from the part number.  Please, please, please stop doing that.