port dffd:
bit0 - bit2 = number of project page
bit3 = for change window of memory
0 = win_1 (c000-ffff)
1 = win_2 (4000-7fff)
bit4 = if 0, then 7ffd is block off and ROM off. in memory 0000 - 3fff is RAM page. win_0.
bit5 = if set in 1 and "ROM14 (bit4 of 7ffd port) = 0, then access WG93 from all memory (0000 - ffff). If ROM14 set to 1, then access to ext memory is change (change hardware acces...new some ports)
bit6 = if set to 1, then ext screen is set in memory area 8000 - bfff. page 6 only (screen). but attributes is stand in 3a page and access from c000 or 4000 (see for bit3).
bit7 = is set to 1, then work ext screen. page 04 = screen0 and page 38 is attr. page 06 screen1 and page 3a is attr.
you can download profi 3+ schematic and see for all. use translators for translate to eng...

---------- Post added at 23:07 ---------- Previous post was at 23:05 ----------

yes
only page 6 (screen), if bit6 = 1. else - 8000 - bfff is not set as window for pages...