Memory Mapping Register

Next Register Number	$8E
Readable	Yes
Writable	Yes
Short Description	Control classic 128K Spectrum memory mapping

   bit 7 = port 0xdffd bit 0         \  RAM
   bits 6:4 = port 0x7ffd bits 2:0   /  bank 0-15
   R bit 3 = 1
   W bit 3 = 1 to change RAM bank,
           = 0 no change to mmu6 / mmu7 / RAM bank in ports 0x7ffd, 0xdffd
   bit 2 = port 0x1ffd bit 0            paging mode
   If bit 2 = paging mode = 0 (normal)
    bit 1 = port 0x1ffd bit 2         \  ROM
    bit 0 = port 0x7ffd bit 4         /  select
   If bit 2 = paging mode = 1 (special allRAM)
    bit 1 = port 0x1ffd bit 2         \  all
    bit 0 = port 0x1ffd bit 1         /  RAM

Writes can affect all ports IO:$7FFD, IO:$DFFD, IO:$1FFD

Writes always change the ROM / allRAM mapping

Writes immediately change the current mmu mapping as if by port write

(new register since core 3.1.1)

(note: Next registers with number higher than $7F are inaccessible from Copper code)