Problem on JTAG debug for ARM920T when mmu/cache is turned on

[#HE XUZHOU#]

I am writing a program for JTAG debug. My target board is ARM920T. I found a single stepping problem when the MMU/CACHE is turn on. If the cache is turn on, single stepping doesn't work. If the cache is turn off, single stepping then works well.I guess this is casued by data/instruction cache. So, I am wandering what I should handle the MMU/CACHE when ARM920T enters debug state with mmu/cache is turned on? I have TWO questions and hope I can get some suggestions here. Thank you!

1. Should I turn off the MMU after ARM920T enter debug state and turn it on before ARM920T is restarted?
2. Should I turn off the cache after ARM920T enter debug state and turn it on before ARM920T is restarted? Or just flush the cahce?