Plus 3 Memory Paging Control: Difference between revisions
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core 3.0 changes |
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! Bit !! Effect | ! 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. | | 2 || Normal mode: High bit of ROM selection. | ||
Revision as of 05:41, 4 October 2019
| Number | PortNumber::$1FFD |
|---|---|
| Decimal | NumberDec:: |
| Short desc. | ShortDesc::Controls ROM paging and special paging options from the +2a/+3. |
| Bit Mask | [[PortMask::%0001 ---- ---- --0-]] |
| Readable | Readable::No |
| Writable | Writable::Yes |
| Subsystem | 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.
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.