[En-Nut-Discussion] xram & banked mem

[Sergey Basmanov]

Where can I find detailed explanation of how external memory works on 
ethernut 2 board?
I'm not familiar with cpld and doesn't understand how it works, so I 
have a few questions:
Why there is a separate address space for each bank select register?
I mean why *(0x8000 + bank) = bank ?
Is it safe to switch bank at any time as I wish or there is some 
limitations by system?
Also, please, point me to a complete memory map of ethernut 2 board.

Thank You.
PS: If possible please answer to e-mail.