[U-Boot] Not able access External peripherals in PPC440EP

[suresh kumar]

Hi,
   I am using a PPC 440EP processor based custom designed board which is
based on AMCC's Yosemite as reference design.
I have ported u-boot-1.1.6 onto it. It is working fine but not able to
access external peripherals like NVRAM, ADC, DAC etc. in the board.
When try to read those addresses with MD command it is generating
exception.
Can anybody please help me how to access them


Regards
Suresh