Prefetch abort exception on TMS570LC4357

Hello,

I got a prefetch abort exception on my TMS570LC4357 MPU. In the Cortex -R5 Revision: r1p2 Technical Reference Manual I found the “Instruction Fault Address Register” (IFAR). I added the code line MRC p15, #0, R0, c6, c0, #2 in order to read the instruction, that caused the prefetch abort. From the IFAR I got the address 0xFF278E68. 
But that didn’t helped because the area is completely zero. According to the Technical Reference Manual, it should be between these two addresses:

DCAN1 RAM     ECC    0xFF1E0000 0xFF1FFFFF
MIBADC2 RAM Parity   0xFF3A0000 0xFF3BFFFF

Did I read the register correctly?

Some more infos:
The HW and SW is tested the whole time with the same test in a loop.
The prefetch abort occurs after various time. For example (sometimes after a 40 minutes run, 1 hour run …)

Does someone have an idea how to locate the problem?
Thanks for any help!