Plus 3 Memory Paging Control: Difference between revisions
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! Bit !! Effect | ! Bit !! Effect | ||
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| 5-7 || Undocumented, may be used for extra bits of slot 4 bank select (see {{PortNo|$7FFD}} | | 5-7 || Undocumented, may be used for extra bits of slot 4 bank select (see {{PortNo|$7FFD}}) | ||
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| 4 || Printer Port Strobe | | 4 || Printer Port Strobe | ||
Revision as of 23:49, 18 August 2017
| Port Number | $1FFD |
|---|---|
| Decimal | |
| Short desc. | Controls ROM paging and special paging options from the +2a/+3. |
| Bit Mask | |
| 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.