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?
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.
Best regards,
Felipe
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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?