Table des matières
INT 0x10 - 0x05 - Select Active Display Page
Request/Call:
| reg | value | descr |
|---|---|---|
| AH | 0x05 | |
| AL | parm | new page number (see Video Pages) |
for PCjr only:
| reg | value | descr |
|---|---|---|
| AL | 0x80 | read CRT/CPU page registers |
| 0x81 | set CPU page register BL: CPU page register |
|
| 0x82 | set CRT page register BH: CRT page register |
|
| 0x83 | set bot CRT and CPU page register BL: CPU page register BH: CRT page register |
- the CPU page determines which 16K block of the first 128K of physical memory will be mapped at B800h by the hardware
- the CRT page determines the start address of the memory used by the video controller
Return (valid only for PCJr)
| reg | descr |
|---|---|
| BH | CRT page register |
| BL | CPU page register |
Notes & Comments
- returns data from BIOS DATA AREA locations 40:50, 40:60 and 40:61
- the 6845 can also be used to read the cursor position
- the return data can be circumvented by direct port I/O to the 6845 CRT Controller since this function returns the data found in the BIOS Data Area without actually checking the controller
- to determine whether the requested page actually exists, use AH=0Fh to query the current page after making this call
