You can think the problem in this way: DSP chip A's 0x4000_0000 is mapped to DSP chip B's 0x1080_0000.
- If you are running loopback mode, then DSP chip A and B is the same chip. So, 0x1080_0000 is the address in same DSP.
- If you are running non-loopback mode, they are different chips. So, this mapping is to another chip DSP B.
Regards, Eric