Addressing on SAMA5D2 Xplained

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3F800000
Posts: 2
Joined: Wed Apr 25, 2018 6:36 pm

Addressing on SAMA5D2 Xplained

Wed Apr 25, 2018 6:53 pm

I'm entirely new to the SAMA5D2 and the eval board.

With the XULT running the provided Linux kernel (blue LED blinking) I used the IDE (IAR EW) to break into debug. The code appears to be running in the address range of 0xC01XXXXX. (Based on the Program Counter and disassembly listings.)

The kernel is identified as: Linux version 4.9.87-linux4sam_5.8 (gcc version 7.3.0 (GCC)

Can someone explain the address space? The data sheet suggests 0xC0000000 is mapped to the "NFC command Register". I was expecting the code to be running in RAM, since U-Boot loads the kernel from flash to 0x22000000. (Even though the datasheet lists that address as in the region of "DDR Chip Select", which also isn't clear.)

Perhaps the answer is the part is using it's MMU and a virtual memory scheme?

Thanks for any insight you can provide.
blue_z
Location: USA
Posts: 1692
Joined: Thu Apr 19, 2007 10:15 pm

Re: Addressing on SAMA5D2 Xplained

Wed Apr 25, 2018 11:29 pm

3F800000 wrote:The code appears to be running in the address range of 0xC01XXXXX.
...
Perhaps the answer is the part is using it's MMU and a virtual memory scheme?
Yes, the addresses you are looking at refer to virtual memory.
When using an "address" you need to be cognizant of which address space it belongs to.
E.G. during the Linux boot, you could be dealing with addresses for NAND flash, physical memory, and virtual memory .

Regards

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