The project that you have built most likely assigned a base address of 0xFFF00000 to the TEMAC. This address falls into the PowerPC's cacheable region. Part of the enabling of caches is first clearing out the caches. This process clears the register settings in the TEMAC.To work around this,change the base address of the TEMAC so that it does not fall into the range of 0xF0000000through 0xFFFFFFFF.