Difference between revisions of "Memory Mapping Register"
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|Readable=Yes | |Readable=Yes | ||
|Writable=Yes | |Writable=Yes | ||
| − | |ShortDesc=Control classic Spectrum memory mapping | + | |ShortDesc=Control classic 128K Spectrum memory mapping |
}} | }} | ||
bit 7 = port 0xdffd bit 0 \ RAM | bit 7 = port 0xdffd bit 0 \ RAM | ||
| − | bits 6:4 = port 0x7ffd bits 2:0 / bank | + | bits 6:4 = port 0x7ffd bits 2:0 / bank 0-15 |
R bit 3 = 1 | R bit 3 = 1 | ||
| − | W bit 3 = 1 to change RAM | + | W bit 3 = 1 to change RAM bank, 0 = no change to mmu6 / mmu7 / RAM bank in ports 0x7ffd, 0xdffd |
bit 2 = port 0x1ffd bit 0 paging mode | bit 2 = port 0x1ffd bit 0 paging mode | ||
If bit 2 = paging mode = 0 (normal) | If bit 2 = paging mode = 0 (normal) | ||
bit 1 = port 0x1ffd bit 2 \ ROM | bit 1 = port 0x1ffd bit 2 \ ROM | ||
bit 0 = port 0x7ffd bit 4 / select | bit 0 = port 0x7ffd bit 4 / select | ||
| − | If bit 2 = paging mode = 1 (special) | + | If bit 2 = paging mode = 1 (special allRAM) |
bit 1 = port 0x1ffd bit 2 \ all | bit 1 = port 0x1ffd bit 2 \ all | ||
bit 0 = port 0x1ffd bit 1 / RAM | bit 0 = port 0x1ffd bit 1 / RAM | ||
Latest revision as of 11:51, 3 November 2024
| Number | $8E |
|---|---|
| Readable | Yes |
| Writable | Yes |
| Short Description | Control classic 128K Spectrum memory mapping |
bit 7 = port 0xdffd bit 0 \ RAM bits 6:4 = port 0x7ffd bits 2:0 / bank 0-15 R bit 3 = 1 W bit 3 = 1 to change RAM bank, 0 = no change to mmu6 / mmu7 / RAM bank in ports 0x7ffd, 0xdffd bit 2 = port 0x1ffd bit 0 paging mode If bit 2 = paging mode = 0 (normal) bit 1 = port 0x1ffd bit 2 \ ROM bit 0 = port 0x7ffd bit 4 / select If bit 2 = paging mode = 1 (special allRAM) bit 1 = port 0x1ffd bit 2 \ all bit 0 = port 0x1ffd bit 1 / RAM
- Writes can affect all ports 0x7ffd, 0xdffd, 0x1ffd
- Writes always change the ROM / allRAM mapping
- Writes immediately change the current mmu mapping as if by port write
(new register since core 3.1.1)
(note: Next registers with number higher than $7F are inaccessible from Copper code)