[U-Boot-Users] Memory Maps

Matias Sundman (AS/EAB) matias.sundman at ericsson.com
Wed Dec 6 12:29:35 CET 2006

In the PowerPC architecture and specifically a Freescale 8270 the HRCW
word decides if U-boot is going to be booted
from regions: HIMEM 0xFE00_0000-0xFFFF_FFFF or LOMEM
0x0000_0000-0x01FF_FFFF. The CIP field decides the
exception vectors; physical address 0xFFFn_nnnn or physical address

Now, in my current board range I have TEXT_BASE as 0xFFF0'0000 and
CFG_FLASH_BASE as 0XFE00'0000. ( 32M )
I my world that makes sense since the flash is mapped in the same range
as the bootloader.

The start.S file says that things will be fine as longs as we configure
BR0 with the same boot ROM link address.
Isn't TEXT_BASE the boot ROM link address?

In one of the TQM boards ( 8260 ) I see that TEXT_BASE is 0x4000'0000
and the FLASH_BASE is 0xFF80'0000.
Here the TEXT_BASE is mapped to a totally different address than
HIMEM/LOMEM, the exception vectors and the 
FLASH_BASE - How is that possible?

In other words - Could someone explain what the relationship is actually
between TEXT_BASE, FLASH_BASE and the 
BR0 register settings are?

Thx // Matias 

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