iMX8 Nano boots from "wrong" device

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iMX8 Nano boots from "wrong" device

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frank_vanhooft
Contributor III

We're seeing a strange (to us) boot behavior with the iMX8 Nano.

We use the boot_mode[3:0] pins to tell the CPU how to boot. We don't touch the internal fuse bits.

When we set the boot_mode pins to 0011 to boot from the external SD card, the CPU boots from the SD card. Great.

When we set the boot_mode pins to 0010 to boot from eMMC, it boots from the external SD card if the eMMC is empty (factory blank, unprogrammed). Only if the eMMC is programmed does it boot from eMMC. 

This is causing some confusion, having it boot from a different memory device than what's been selected. Having it boot from SD when eMMC is selected is quite unexpected (to us).

Is it expected that it would boot from external SD in this situation? The iMX8 Nano reference manual, figure 6.1, does not appear to show this behavior.

Any clarifications would be appreciated. Thanks.

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igorpadykov
NXP TechSupport
NXP TechSupport

Hi frank_vanhooft

 

such behaviour may be related to manufacture mode described in

Figure 6-2, sect.6.1.11 SD/MMC manufacture mode

i.MX 8M Mini Applications Processor Reference Manual

 

Best regards
igor

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