Arm Development Studio forum Testing Data Cache of ARM926EJ-S

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Testing Data Cache of ARM926EJ-S

Note: This was originally posted on 26th November 2009 at http://forums.arm.com

Hi,
I have an issue testing data cache for ARM926EJ-S used by AT91SAM9XE and AT91SAM9G20.
As you know, AT91SAM9XE has the flash memory and in this case I'm trying to test data cache of the architecture, in these conditions:
1. MMU and Page Table enabled
2. Round Robin replacement enabled
3. The code of the main program is loaded in the flash memory
4. The data pattern for the test are read and written in SDRAM
Under these conditions the result of the test for data cache is good.

When I use the AT91SAM9G20, that no have flash memory on board, I'm constrained to load the code of the main program in another memory.
In the first case I choose to load the main program, in the SDRAM, and I try to test data cache of the architecture, in these conditions:
1. MMU and Page Table enabled
2. Round Robin replacement enabled
3. The code of the main program is loaded in SDRAM
4. The data pattern for the test are read and written in SDRAM
The result in this case is a cache fault.

In the second mode of AT91SAM9G20, I choose to load the code of main program in one of the two SRAM region, while the data pattern are read and written always in SDRAM.
Well, in this case, the same test works properly.

I want to know if someone have this problem and why if I load in the same memory (SDRAM) instructions and data, the test fails.
Is there a particular reason?

Thanks in advance for your help