PowerPC simulator

I am a new user of eCos. I tried to use the PowerPC simulator available and
could run the example programs using GDB with simulator target without
any problem.  I find that the simulator is using the 60x variants of PowerPC .
I tried to change the simulator to include PPC40x variant and could
build the example
programs successfully.

But while trying to run , I get the error message
core_find_mapping() - access to unmaped address, attach a default map
to handle this -

I called the simulator with
target sim -o '/iobus/pal@0xf0001000/reg 0xf0001000 32'

like the earlier configuration...

Kindly help

Bindu Thomas