Can SAMA5D27 ROM code boot from SD card with i bit interface?

Discussion around products based on ARM Cortex-A5 core.

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nancyb
Posts: 3
Joined: Mon Oct 08, 2018 12:28 pm

Can SAMA5D27 ROM code boot from SD card with i bit interface?

Thu Apr 11, 2019 11:21 am

I am debugging a custom board based on the SAMA5D27 SOM1 Kit1 design. The Kit1 board implements a 4 bit SD card interface and my custom board implements a 1 bit interface. I created a Linux bootable SD card that I verified boots on the Kit1 board and does not boot on my custom board. I verified the ROM code is clocking the SD card. The application code can access the SD card through the 1 bit interface.

Can SAMA5D27 ROM code boot from an SD card with i bit interface?
blue_z
Location: USA
Posts: 1924
Joined: Thu Apr 19, 2007 10:15 pm

Re: Can SAMA5D27 ROM code boot from SD card with i bit interface?

Fri Apr 12, 2019 11:39 pm

nancyb wrote: Can SAMA5D27 ROM code boot from an SD card with i bit interface?
What is an "i bit interface"?

nancyb wrote: ... my custom board implements a 1 bit interface ... and does not boot
You probably already know the reason why this fails, but are hoping for a get-out-of-jail card.
Since the SoC ROM code is proprietary and not published, only Microchip Tech Support can provide a definitive answer.

Regards
nancyb
Posts: 3
Joined: Mon Oct 08, 2018 12:28 pm

Re: Can SAMA5D27 ROM code boot from SD card with i bit interface?

Mon Apr 15, 2019 11:14 am

"i bit" is a typo. Should be 1 bit.

You are wrong; I do not need a get-out-of-jail card. You did obliquely answer my question, however. Now I understand why I could not find the answer to my question in any public documentation.
thackerp
Posts: 11
Joined: Tue Jul 19, 2016 10:19 pm

Re: Can SAMA5D27 ROM code boot from SD card with i bit interface?

Mon Apr 15, 2019 6:36 pm

The document linked below well describes the boot procedure and should answer your questions.

https://www.microchip.com/wwwAppNotes/A ... e=en607377
nancyb
Posts: 3
Joined: Mon Oct 08, 2018 12:28 pm

Re: Can SAMA5D27 ROM code boot from SD card with i bit interface?

Tue Apr 16, 2019 12:09 pm

Yesterday while debugging I discovered that RomBOOT had loaded my image from the SD card using the 1-bit interface. I was pleasantly surprised to find my code running in SRAM.

Thank you, thackerp. Your linked document answered my question and confirmed that RomBOOT supports a 1-bit SD card interface.

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