RTCfile question for LPC18XX

[daweiyou]

Hi :

Here is one question for LPC1875, I found unused Regfiles registers are random value.

But from user manuel, the reset value is 0x00 all. I verified this situation on LPC1857 MCB board.

Does someone experience this situation? and know why? thx

[rolfmeeser]

The REGFILEx registers are backup registers in the VBAT domain. You use them to store data that shall be maintained through power cycles of the device as long as the backup battery is there.

So by their very nature these registers do not have a defined reset value. After a backup battery failure they are expected to hold random values.

[kerryzhou]

Hi Dawei,

I found you are our colleague, and you already post this question in our internal community:RTCfile question for LPC18XX

That place is for our internal question discussion with AE department, so, please refer to our AE's answer, after AE give the correct answer, please post it in this area for the external customer reference.

In the meanwhile, I will also test it on my side.

Jingjing

[daweiyou]

thx

[kerryzhou]

Hi Dawei,

    Could you tell me which register are random value in your side?

  I have test it on my side, this is the picture from LPCopen IAR project:

  The unused register is 0, so please tell me the detail register which have random data on your side .

Have a great day,

Jingjing

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[daweiyou]

Hi Jingjing:

it's REGFiles register:

[kerryzhou]

Hi Dawei,

    Thank you for your more details and I can reproduce it now.

    I think the data in the MCBLPC1800 is the RNG key data, from the user manual, page96

Actually, I also tried to mass erase the chip in the MCB LPC1800 board, after power on, check 0X40041000, it still have the same data, and the chip is running the board's out factory code which may from the external flash.

  So, I think it may relate to the RNG KEY random data, but for detials, when it is wrote,  and why reset the data can't be 0, I need to contact with the AE department.

  After I get the answer from the AE department,  I will let you know.

  So, please wait patiently.

Have a great day,
Jingjing

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