Difference between revisions of "83:Ports:02"
From WikiTI
(→Write Values: - corrected an error; some bits were swapped) |
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* Bits 0 to 2: The lower 3 bits of the desired ROM page (bit 3 can be set through bit 4 of the [[83:Ports:00|link port]]) | * Bits 0 to 2: The lower 3 bits of the desired ROM page (bit 3 can be set through bit 4 of the [[83:Ports:00|link port]]) | ||
* Bit 3: Must be 1, otherwise the the calculator crashes | * Bit 3: Must be 1, otherwise the the calculator crashes | ||
| − | * Bit 4: | + | * Bit 4: Unknown, harmless |
* Bit 5: Unknown, harmless | * Bit 5: Unknown, harmless | ||
| − | * Bit 6: | + | * Bit 6: 0 - the specified ROM page is swapped in, 1 - the RAM page specified by bit 0 swapped in (0 causes it to mirror the page at C000h, 1 mirrors the page at 8000h) |
* Bit 7: Must be 1, otherwise the the calculator crashes | * Bit 7: Must be 1, otherwise the the calculator crashes | ||
Revision as of 14:03, 4 April 2005
Synopsis
Port Number: 02h
Function: ROM and RAM Pager
This port controls what page is swapped into the 4000h to 7FFFh range.
Read Values
Always the last value output is read back.
Write Values
- Bits 0 to 2: The lower 3 bits of the desired ROM page (bit 3 can be set through bit 4 of the link port)
- Bit 3: Must be 1, otherwise the the calculator crashes
- Bit 4: Unknown, harmless
- Bit 5: Unknown, harmless
- Bit 6: 0 - the specified ROM page is swapped in, 1 - the RAM page specified by bit 0 swapped in (0 causes it to mirror the page at C000h, 1 mirrors the page at 8000h)
- Bit 7: Must be 1, otherwise the the calculator crashes
Credits and Contributions
- created by CoBB
