Question : In the C54x itself, in the ROM there is a bist code that can be used by customers. It starts in FF00h (when looping and toggles XF if the result is OK) or starts in FF01h (when called as a function returning 0 in AR7 if result is OK). It tests the memory and the CPU. Is this a selftest and diagnostics code for the C54x to test opcode, maybe memory.

Answer : I would hesitate to call this code at FF00 Built-In-Self-Test. If it is the same code that I have seen, it is code that the product engineers use for Life-Testing the device(...what I prefer to call BILT - Built-In-Life-Test). If it's the code I think it is, there is no method of providing a CRC or anything else to ensure that the contents of the memory are correct(or even populated). It also goes through many math functions trying to exercise the various parts of the core, but doesn't verify the PROPER functioning of these. I think you can verify functionality IFF you are connected to the tester and can scan the PSA back out of the device at its completion.