Difference between revisions of "InstallRAMISR"
From MSX Game Library
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Warnings: | Warnings: | ||
* This option only work on MSX with at least 64 KB of RAM (otherwise, there is no RAM on page #0). | * This option only work on MSX with at least 64 KB of RAM (otherwise, there is no RAM on page #0). | ||
| + | * The ISR is installed from 0038h to 005Eh but it is recommended to don't use the first 256 bytes for future iteration. So, please start using page #0 RAM from 0100h. | ||
* Obviously, no BIOS function can be used in this program (unless you reswitched the Main-ROM on page #0 first). | * Obviously, no BIOS function can be used in this program (unless you reswitched the Main-ROM on page #0 first). | ||
| + | |||
| + | You can check the [[Samples#Software_Sprite|Software Sprite]] sample program for a use example. | ||
Latest revision as of 00:05, 9 June 2022
This Build tool option allow cartridge program to use page #0 (address 0000h~3FFFh) as RAM. This gives almost 16 KB more memory.
:: Set RAM in slot 0 and install ISR there (0=false, 1=true) set InstallRAMISR=1
If InstallRAMISR is set to 1, the cartridge boot code will automatically switch page #0 to the same slot as page #3 (where RAM is located), then copy a ISR (Interrupt Service Routine) at address 0038h. This ISR handle VDP's V-Blank interruption (each 50/60 Hz) and call an handler function that program must provide: void VDP_InterruptHandler();
Warnings:
- This option only work on MSX with at least 64 KB of RAM (otherwise, there is no RAM on page #0).
- The ISR is installed from 0038h to 005Eh but it is recommended to don't use the first 256 bytes for future iteration. So, please start using page #0 RAM from 0100h.
- Obviously, no BIOS function can be used in this program (unless you reswitched the Main-ROM on page #0 first).
You can check the Software Sprite sample program for a use example.