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Newbie -- Accessing Hardware Ports

Okay, I have managed to get 'hello world' to work under both psim and 
on a PPC2A using the ppcn_60x BSP.  Now I am trying to branch out and 
exercise the board by flashing some LEDs.  Code snip looks something 

    volatile unsigned8 *pLED_Control;

    pLED_Control = (unsigned8 *) 0x00000860;

        *pLED_Control = 0x0F;
        /**  wait loop  **/
        *pLED_Control - 0x00;  /** LEDs should blink on & off  **/

Unfortunately, nothing happens.  I have also tried reading some board 
configuration locations (8-bit) and got back values that are no where 
near what they should be.  

Now I have concluded the problem is one of the following, but have not 
been able to find documentation to support or refute the position:

1)  RTEMS does not allow direct manipulation of hardware ports via 
pointers.  (But there has got to be a way around this as the COM port 

2)  That region of memory is being cached.  In which case I need to 
figure out how to access the hardware registers to keep that region 
from being cashed.

3)  I have screwed up basic C code.

4)  There is a board configuration problem.

Anybody willing to hazard a guess as to which is the most likely