Memory Paging Control
|Short desc.||Selects active RAM, ROM, and displayed screen.|
|Bit Mask||%01-- ---- ---- --0-|
Selects the active memory page in slot 4 at $C000. See Memory map.
Any values written to this port should also be stored at $5B5C if any OS routines are in use.
|5||Lock memory paging (setting to 1 locks pages and cannot be unlocked until next reset)|
|4||ROM select (low bit of ROM select on +2/+3)|
|3||Shadow Screen toggle
When 1, the "Layer 2" is disabled due to ULA screen being read from other memory bank. For double-buffered ULA screen together with Layer 2 functionality the Timex Sinclair Video Mode Control ($xxFF / 255) is suggested.
|0-2||Bank number for slot 4 ($C000)|