topic Re: What is SW_GP1 purpose in i.MX RT 10xx family? in i.MX RT Crossover MCUs

What is SW_GP1 purpose in i.MX RT 10xx family?

embeddedev — Thu, 15 Jul 2021 09:06:36 GMT

Could you tell me please what is the purpose of SW_GP1 and how can be used?

I understand that SW_GP2 (128 bits) can be used as AES128 key hardwired to DCP and BEE hardware module but I did not find anything in the documentation related to SW_GP1 (32 bit).
What is the difference between GP1 and SW_GP1? Beside general purpose usage, is there any special usage of SW_GP1 similar to SW_GP2?

Thank you for your support.

Re: What is SW_GP1 purpose in i.MX RT 10xx family?

FelipeGarcia — Fri, 16 Jul 2021 15:27:50 GMT

Hi,

SW_GP1 is a space in efuses to store keys. However, other than the size (32 bit) the other difference is that SW_GP1 cannot be used as AES key as is not supported as a key selection in the BEE module.

Best regards,

Felipe

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Re: What is SW_GP1 purpose in i.MX RT 10xx family?

embeddedev — Mon, 26 Jul 2021 06:42:27 GMT

Thank you Felipe for your reply. Do you know how to use SW_GP1 when it is locked by SW_GP1_LOCK? I mean, if this key is not hardwired to any crypto module then how could somebody use it when locked by SW_GP1_LOCK?

Re: What is SW_GP1 purpose in i.MX RT 10xx family?

FelipeGarcia — Wed, 28 Jul 2021 21:33:03 GMT

Hi,

You can use it using fuse shadow memory footprint.

There is an specific location in OCOTP memory map that reflects the value of SW_GP1.

Best regards,

Felipe

Re: What is SW_GP1 purpose in i.MX RT 10xx family?

embeddedev — Thu, 29 Jul 2021 07:41:17 GMT

Meanwhile I found following: "The SW_GP1 fuse doesn’t have a pre-defined purpose and isn’t hardwired to any of the crypto blocks. The SW_GP1_LOCK bit is a write and overwrite protection, so when it is set you can still read back the fuse value and use it (SW_GP1_LOCK isn’t a read lock)."

Re: What is SW_GP1 purpose in i.MX RT 10xx family?

stefanct — Sat, 12 Jul 2025 00:13:30 GMT

One funny thing I just noticed: The low byte reads as 0xFF if I set EFUSE_PROG_SUPPLY_GATE. This makes as much sense as the documentation on this flag: nada.

The other 0x*80 fuses at 0x580 and 0x680 show the same behavior but are reserved.