Difference between revisions of "Plus 3 Memory Paging Control"
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{{Port | {{Port | ||
|Number=$1FFD | |Number=$1FFD | ||
| + | |NumberDec=8189 | ||
| + | |PortMask=%0001 ---- ---- --0- | ||
|ShortDesc=Controls ROM paging and special paging options from the +2a/+3. | |ShortDesc=Controls ROM paging and special paging options from the +2a/+3. | ||
|Readable=No | |Readable=No | ||
|Writable=Yes | |Writable=Yes | ||
|Subsystem=Memory map | |Subsystem=Memory map | ||
| − | |||
}} | }} | ||
Bit mapped to control paging options. | Bit mapped to control paging options. | ||
| Line 14: | Line 15: | ||
| 7-3 || Unused, use 0 (Printer Port Strobe b4 and Disk motor enable b3 are not implemented in core3.0) | | 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. 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]]). | Special mode: High bit of memory configuration number (see [[Memory map]]). | ||
Latest revision as of 11:17, 4 May 2020
| Number | $1FFD |
|---|---|
| Decimal | 8189 |
| 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.