diff options
Diffstat (limited to 'boot1/video.asm')
| -rw-r--r-- | boot1/video.asm | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/boot1/video.asm b/boot1/video.asm new file mode 100644 index 0000000..61ff153 --- /dev/null +++ b/boot1/video.asm @@ -0,0 +1,81 @@ +;;; Display the ASCIIZ string at ds:si via BIOS VIDEO call (real mode only) +Write: + lodsb ; load char to al, increment si + or al, al ; see if it's null + jz .DONE ; if so, we're finished + mov ah, 0x0E ; service 0x0E: output one char + mov bh, 0x00 ; display page 0 + mov bl, 0x07 ; char text attrib (white on black) + int 0x10 ; invoke bios + jmp Write ; next char +.DONE: + ret + +;;; Probe the video system of the machine via BIOS VIDEO calls, populate +;;; the HARDWARE_INFO buffer (real mode only). +PROBE_VIDEO: + ;; identify the display type + call DISP_ID + mov [bDisplayType], al + + ;; determine the font size + call FONT_SIZE + mov [bFontSize], al + ret + +;;; Determine the font size (width in pixels) of the current display. +FONT_SIZE: + cmp al, 0x0a + jl .TRY_OLD + mov al, BYTE 16 + ret +.TRY_OLD: + cmp al, BYTE 1 + jne .TRY_CGA + mov al, BYTE 14 + ret +.TRY_CGA: + cmp al, BYTE 2 + jne .TRY_VGA + mov al, BYTE 8 + ret +.TRY_VGA: + mov ah, 0x11 + mov al, 0x30 + mov bh, 0 + int 0x10 + mov al, cl + ret + +;;; Determine the video type via BIOS VIDEO call +DISP_ID: + xor ax, ax + mov ah, 0x1a + int 0x10 + cmp al, 0x1a + jne .TRY_EGA + mov al, bl + ret +.TRY_EGA: + mov ah, 0x12 + mov bx, 0x10 + int 0x10 + cmp bx, 0x10 + je .OLD_BOARDS + cmp bh, 0 + je .EGA_COLOR + mov al, 5 + ret +.EGA_COLOR: + mov al, 4 + ret +.OLD_BOARDS: + int 0x11 + and al, 0x30 + cmp al, 0x30 + jne .CGA + mov al, 1 + ret +.CGA: + mov al, 2 + ret |