MBX boot loader on a MPC8260 custom board

Julien Eyries julien.eyries at thales-bm.com
Thu Mar 21 21:53:23 EST 2002

hi all ,

we have here a custom MPC8260 board (4 Mo flash, 32 Mo SDRAM,200 Mhz
MPC8260) and we want to use the HardHat linux from Montavista.
we are also using BDI-2000 probe (from ABATRON) .

the kernel we have build is based on the ADS8260 board which is quite
similar to our board.

the boot-loader we use is the "mbx" boot loader which come with the
Linux kernel tree.

the problem i have is :
- we load the file "zvmlinux.mbx" using the BDI2000 probe
- we take control over the MPC8260 with "ppc_82xx-gdb zvmlinux.mbx" and
"target remote xx.xx.xx.xx:2001"
- we do some "stepi" and the code runs, entering function
"decompress_kernel", then "serial_init" .
- at some point in this function "serial_init" , the PC (program
counter) begins to count downwards !!! for exemple ( 0x400000 ...
0x3ffffc ... 0x3fff8 ...  )

another point is: when debugging C source code (in emacs + gdb),
we can see that the programms jumps from one point to another (some
times backward) , not following the logical flow of the C source code
.Is that normal ????

what could be the reason of such behaviour ???
does someone here have an idea for our problem ?????

any help is welcome,

Julien Eyries
R&D engineer
Thales Broadcast & Multimedia (ex-thomcast)
email: julien.eyries at thales-bm.com
fax: 33(0) 1 34 90 31 10
tel: 33(0) 1 34 90 31 01

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