RT1050 Encrypted XIP example sets BEE_KEY0_SEL to a reserved value?

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RT1050 Encrypted XIP example sets BEE_KEY0_SEL to a reserved value?

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rshipman
Contributor V

Document: AN12079.pdf: How to use i.MXRT Security Boot, Application Notes, Rev. 0, 10/2017

Section: 3.3.2. Generate SB file for FlexSPI NOR image encryption and programming

Pages: 25-27

The example .bd file contains the lines:

#6. Program BEE_KEY0_SEL and BEE_KEY1_SEL

load fuse 0x0000e000 > 0x06;

Which sets:

BEE_KEY0_SEL to 10 = Reserved

BEE_KEY1_SEL to 11 = From SW-GP2

Why is BEE_KEY0_SEL being set to a reserved value?

Presumably only bit 1 of these two fields (i.e. bits 0x460[13] and 0x460[15]) are actually observed by the ROM bootloader?

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FelipeGarcia
NXP TechSupport
NXP TechSupport

Hi Ronnie,

 

I am sorry for the late response. We have been under a big workload.

 

Actually, you are not loading 0x6 to the fuse you are loading 0xE000. This means you are setting bit 13, 14 and 15. Which is:

 

BEE_KEY0_SEL = From OTPMK

BEE_KEY1_SEL = From SW-GP2

 

Please check table 3-10 eFUSE Configuration for Encrypted XIP from Secure Reference Manual.

 

0x6 is referring to the OTP bank address.

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Best regards,

Felipe

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rshipman
Contributor V

See also:

Document: AN12079.pdf: How to use i.MXRT Security Boot, Application Notes, Rev. 0, 10/2017

Section: 2.5. Encrypt XIP flow

Pages: 10

Figure 8. Encrypt XIP Flow

This diagram shows that decisions are based on BT_KEY0_SEL and BT_KEY1_SEL being non-zero. (So why are these fields 2-bits wide?)

Why is the example .bd file setting the two fields differently?

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