Memory Paging Control

Number	PortNumber::$7FFD
Decimal	NumberDec::
Short desc.	ShortDesc::Selects active RAM, ROM, and displayed screen.
Bit Mask	PortMask::
Readable	Readable::No
Writable	Writable::Yes
Subsystem	Subsystem::Memory map

Selects the active memory page in slot 4 at $C000. See Memory map.

Any values written to this port should also be stored at $5B5C if any OS routines are in use.

Bit	Effect
6-7	Undocumented
5	Lock memory paging (setting to 1 locks pages and cannot be unlocked until next reset)
4	ROM select (low bit of ROM select on +2/+3)
3	Shadow Screen toggle
0-2	Bank number for slot 4 ($C000)