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Frater 2026-01-08 10:26:52 +01:00
commit 08f66b73e1
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src/bda.asm Normal file
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;
; https://wiki.nox-rhea.org/back2root/ibm-pc-ms-dos/hardware/informations/bios_data_area
;
%define BDA_SEGMENT 0x0040 ; segment BDA
; custom var
%define BDA_INFO_MEM_SIZE 0x0014 ; Memory size in Kbytes
%define BDA_INFO_MEM_SEG BDA_INFO_MEM_SIZE+2 ; highest Memory Segment
%define BDA_MOUSE_BUFFER 0x0068 ; dword
%define BDA_MOUSE_IDX BDA_MOUSE_BUFFER+4 ; byte
%define BDA_MOUSE_X BDA_MOUSE_BUFFER+5 ; word
%define BDA_MOUSE_Y BDA_MOUSE_BUFFER+7 ; word
; video related information (compatible with VGA bios)
%define BDA_VIDEO_CURR_MODE 0x0049
%define BDA_VIDEO_COLUMNS 0x004A
%define BDA_VIDEO_BUF_SIZE 0x004C
%define BDA_VIDEO_OFS_PAGE 0x004E
; 40:50 8 words Cursor position of pages 1-8, high order byte=row low order byte=column; changing this data isn't reflected immediately on the display
; 40:60 byte Cursor ending (bottom) scan line (don't modify)
; 40:61 byte Cursor starting (top) scan line (don't modify)
; 40:62 byte Active display page number
; 40:63 word Base port address for active 6845 CRT controller 3B4h = mono, 3D4h = color
; 40:65 byte 6845 CRT mode control register value (port 3x8h) ; EGA/VGA values emulate those of the MDA/CGA
; 40:66 byte CGA current color palette mask setting (port 3d9h) ; EGA and VGA values emulate the CGA