MPC834x global timers question

[Bruce_Leonard at selinc.com]

I know this isn't the right forum for this but I can't seem to find a 
generic PPC mailing list.

I'm trying to get a global timer going on an MPC834x, and the way I learn 
is to just play with HW, so I've got an Abatron BDI2K hooked up to my 
processor so I can just manipulate registers without having to deal with 
writing code.  However, I seem to be unable to modify certain registers in 
the global timers with this set up and I don't understand why. 
Specifically, if a register has a bit that's a '1' following a reset, I 
can't change that bit to a '0'.  This is happening with the Global Timers 
Reference Registers (GTRFR1 - 4) and the Global Timers Prescale Registers 
(GTPSR1 - 4).  The reset state of the GTRFRs is 0xFFFF and I can't change 
it to any other value.  The reset state of the GTPSRs is 0x3 and I can't 
clear the 2 LSB.  I can change any other bits in the prescale registers, 
but not the two which are a '1' at reset.

Has anyone else seen this behavior?

Bruce