I have two query to understand Genode basics.

I am not able to understand the explanation given for Bitfield at line #140 in 

repos/base/include/util/register.h

" Bitfields are read and written according to their range, so if we have a 'Bitfield<2,3>' and write '0b11101' to it  only '0b101' (shiftet by 2 bits) is written."

can any body explain me what it means for ?

I was trying to understand implemented TZASC driver in Genode for vea9x4 board.

can you suggest me some sources which have information used in 

repos/os/src/server/tz_vmm/vea9x4/tsc_380.h

Regards 

Franc