[U-Boot-Users] boot up u-boot from RAM

[Lei Sun]

I did build my code to 0x0 (TEXT_BASE=0x0). Your explaination does
make some sense, but what i don't understand is that upon reset, PC
jump to reset vector 0x100, does it need a  valid instruction on 0x100
to exectute, so why couldn't I single step start from this location?
Have you ever tried to put the code to 0x0 instead ? It didn't work?
Why would it work if in the flash? in that case the the initial
portion of the flash is also for exeption vectors.

On 10/26/06, Nghiem, Tien <TNghiem at oerlikon.ca> wrote:
> Lei,
>
> You have to rebuild your code to put your code in the RAM area (other than the FLASH area). Don't use the address 0x00-0x2fff because its reserved for the exception vectors usually. I have a Lite5200 EVB. I use the address 0x20000 to put my u-boot in RAM and it works. I don't know if it could be done for the mpc8270.
>
> Tien
>
> -----Original Message-----
> From: u-boot-users-bounces at lists.sourceforge.net
> [mailto:u-boot-users-bounces at lists.sourceforge.net]On Behalf Of Lei Sun
> Sent: Thursday, October 26, 2006 4:15 PM
> To: u-boot-users at lists.sourceforge.net
> Subject: [U-Boot-Users] boot up u-boot from RAM
>
>
> Hi all:
>   I am debugging a costomized board based on mpc8270, due to the
> design flaw, we can't boot up the system using flash, so I was trying
> to debug u-boot by loading it into the RAM.
>  I used JTAG debugger to initialize the SDRAM and load the u-boot to
> 0x0, after reset, the PC is at 0x100. the disassembled code looks
> correct on that location, however, i can't single step start from
> 0x100. Is that because 0x100 is the reset vector ? I tried to put some
> breakpoint at some places not far from start point, but it gave me
> "unknown halt at 0x00000000" error after "run" command. after that the
> memory seems corrupted.
>  Too bad I was using a bad debugger(Guardian-SE),  I have a
> evaluation copy of the codewarrior plus USB+TAP from freescale. I
> tried that on our PQ2FADS-VR SDK. After reset, and CPU halt, I can't
> see any disassembed code on 0x100 (the uboot is already in the flash,
> and I assume it should read data from CS0 upon reset). Although the
> code does execute after hitting "run" button.  I wonder why can't I
> see the disassembed code after reset?
>
> Thanks
> lei
>
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