MBX boot loader on a MPC8260 custom board

[Julien Eyries]

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,
greetings,



--
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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