Plus 3 Memory Paging Control

Port Number	$1FFD
Decimal
Short desc.	Controls ROM paging and special paging options from the +2a/+3.
Bit Mask	%0001 ---- ---- --0-
Readable	No
Writable	Yes
Subsystem	Memory map

Bit mapped to control paging options.

Bit	Effect
5-7	Undocumented, may be used for extra bits of slot 4 bank select (see NextPort:$7FFD)
4	Printer Port Strobe
3	Disk motor enable
2	Normal mode: High bit of ROM selection. Special mode: High bit of memory configuration number (see Memory map).
1	Special mode: Low bit of memory configuration number.
0	Paging mode. 0=Normal, 1=Special.

Any values written to this port should also be stored in $5B67 if you intend to use any OS routines.