Plus 3 Memory Paging Control
From SpecNext Wiki
| Number | PortNumber::$1FFD |
|---|---|
| Decimal | NumberDec:: |
| Short desc. | ShortDesc::Controls ROM paging and special paging options from the +2a/+3. |
| Bit Mask | PortMask:: |
| Readable | Readable::No |
| Writable | Writable::Yes |
| Subsystem | Subsystem::Memory map |
Bit mapped to control paging options.
| Bit | Effect |
|---|---|
| 5-7 | Undocumented |
| 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.