OpenSpectrum Wiki
[ main ][ links ][ about ][ help ][ discussions ][ projects ]Four lines will identify to the RAM/ROM selector which RAM/ROM mode to select.
MODE0,MODE1,MODE2,MODE3 will define 1 of 16 modes.
MEMRQ, RD and RW will synchronise the operation.
| Page0 | Notes | RAM Page addr | ROM Page addr | Technical Notes | Thoughts. | |
| RAM | External ROMCS | - | - | No internal access, external ROM selected. | ||
| 1 | RAM | 74000H | - | ALL RAM in memory. | ||
| 2 | RAM | 78000H | - | ALL RAM in memory. | ||
| 3 | RAM | 7C000H | - | ALL RAM in memory. | ||
| 4 | RORAM | Read Only Ram | 70000H | - | Ram Write Protected | |
| 5 | RORAM | Read Only Ram | 74000H | - | Ram Write Protected | |
| 6 | RORAM | Read Only Ram | 78000H | - | Ram Write Protected | |
| 7 | RORAM | Read Only Ram | 7C000H | - | Ram Write Protected | |
| 8 | ROM | 16K ROM | - | 0000H | 16K ROM / 16K RAM | |
| 9 | ROM | 48K ROM | - | 0000H | 48K(16K) ROM | |
| 10 | ROM | 128K ROM | - | 4000H | 128K Base ROM | |
| 11 | ROM | - | 8000H | Not yet certain what to put here. | ||
| 12 | RAM/ROM | Microdrive ROM | 70000H | C000H | Page In/Out on memory location | |
| 13 | RAM/ROM | Multiface ROM | 74000H | E000H | Page In/Out on NMI | |
| 14 | RORAM/ROM | Non-Specific | 70000H | - | RAM Half Write Protected. Memory Page In | |
| 15 | RORAM/ROM | Non-Specific | 74000H | - | RAM Half Write Protected. NMI Page In. |