ROM version has a size of 256K. It is split into 16K pages. 2 Pages are standard CPC roms, one of which is a "extension rom".
Part of the Brunword word processor is copied into RAM, the "extension rom" does most of this.
Part of the Brunword word processor is copied into RAM. This is done by it's "extension rom". The ROM Select port (&DF00) is decoded and has 2 roles. First is to select which ROM page appears in the range &C000-&FFFF of the Z80's address space.(It seems bit 7,6,5,4 must be 0).Bits 3..0 are decoded as the page number. Page 1 and 2 only seem to be visible at this time.
The second role (when bit 5,4 are used), makes a page visible in the range &4000-&FFFF of the Z80's address space.
Bit 5 seems to be rom enable/disable, bit 4 is set for the second role (0 for other), and bits 3..0 are the page number.
The exact decoding of the ROM select port is unknown.