Plus 3 Memory Paging Control
From SpecNext official Wiki
| 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 |
|---|---|
| 7-3 | Unused, use 0 (Printer Port Strobe b4 and Disk motor enable b3 are not implemented in core3.0) |
| 2 | Normal mode: High bit of ROM selection. Together with bit 4 from $7FFD port:
00 = ROM0 = 128K editor and menu system 01 = ROM1 = 128K syntax checker 10 = ROM2 = +3DOS 11 = ROM3 = 48K BASIC 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.
NEW in core 3.0:
When exiting +3 special paging mode, the banks 5 and 2 are mapped back at regular place.