PC Graphics Unleashed/PC Graphics Unleashed.iso/ch01/aheada.asm

Assembly Source File | 1991-03-20 | 4KB | 217 lines

; This is file AHEADA.ASM
;
; Copyright (C) 1991 DJ Delorie, 24 Kirsten Ave, Rochester NH 03867-2954
;
; This file is distributed under the terms listed in the document
; "copying.dj", available from DJ Delorie at the address above.
; A copy of "copying.dj" should accompany this file; if not, a copy
; should be available from where this file was obtained.  This file
; may not be distributed without a verbatim copy of "copying.dj".
;
; This file is distributed WITHOUT ANY WARRANTY; without even the implied
; warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
;

cseg    segment    byte public 'code'
    assume    cs:cseg, ds:cseg, es:cseg, ss:nothing

    dw    offset init_routine
    dw    offset paging_routine
    dw    0    ; set to 1 if separate read & write windows or
            ; only 64K of video RAM (ie: no paging)

def_tw    dw    80    ; filled in by go32 if GO32 env. var. is set
def_th    dw    25
def_gw    dw    640
def_gh    dw    480

;--------------------------------------------------------------------------
; Entry: AX=mode selection
;        0=80x25 text
;        1=default text
;        2=text CX cols by DX rows
;        3=biggest text
;        4=320x200 graphics
;        5=default graphics
;        6=graphics CX width by DX height
;        7=biggest non-interlaced graphics
;        8=biggest graphics
;
; NOTE: This runs in real mode, but don't mess with the segment registers.
;
; Exit:  CX=width (in pixels or characters)
;        DX=height

init_table    label    word
    dw    offset init_0
    dw    offset init_1
    dw    offset init_2
    dw    offset init_3
    dw    offset init_4
    dw    offset init_5
    dw    offset init_6
    dw    offset init_7
    dw    offset init_8

init_routine    proc    far
    cmp    ax,8
    jbe    valid_req
    ret
valid_req:
    shl    ax,1
    mov    bx,ax
    jmp    init_table[bx]

init_0: ; 80x25 text
    mov    ax,3
    int    10h
    mov    cx,80
    mov    dx,25
    ret

init_1: ; default text
    mov    cx,def_tw
    mov    dx,def_th
    jmp    init_2

init_2_table    label    word
    dw    01h, 40, 25
    dw    03h, 80, 25
init_2_tend    label    word

init_2: ; CX*DX text
    mov    si,offset init_2_table
init_2a:
    cmp    [si+2],cx
    jb    init_2b
    cmp    [si+4],dx
    jb    init_2b
    ; got a big enough one!
    jmp    init_2c
init_2b:
    cmp    si,offset init_2_tend - 6
    je    init_2c
    add    si,6
    jmp    init_2a
init_2c:
    mov    ax,[si]
    push    si
    int    10h
    pop    si
    mov    cx,[si+2]
    mov    dx,[si+4]
    ret

init_3: ; biggest text
    mov    ax,[init_2_tend-6]
    int    10h
    mov    cx,[init_2_tend-4]
    mov    dx,[init_2_tend-2]
    ret

init_4: ; 320x200 graphics
    mov    ax,13h
    int    10h
    mov    cx,320
    mov    dx,200
    ret

init_5: ; default graphics - should be 640x480 if supported
    mov    cx,def_gw
    mov    dx,def_gh
    jmp    init_6

init_6_table    label    word
    dw    13h, 320, 200
    dw    60h, 640, 400
    dw    61h, 640, 480
    dw    62h, 800, 600
init_6_tend    label    word

init_6: ; CX*DX graphics
    mov    si,offset init_6_table
init_6a:
    cmp    [si+2],cx
    jb    init_6b
    cmp    [si+4],dx
    jb    init_6b
    ; got a big enough one!
    jmp    init_6c
init_6b:
    cmp    si,offset init_6_tend - 6
    je    init_6c
    add    si,6
    jmp    init_6a
init_6c:
    mov    ax,[si]
    push    si
    int    10h
    pop    si
    mov    cx,[si+2]
    mov    dx,[si+4]
    ret

init_7: ; biggest non-interlaced graphics
    mov    ax,62h
    int    10h
    mov    cx,800
    mov    dx,600
    ret

init_8: ; biggest graphics
    mov    ax,62h
    int    10h
    mov    cx,800
    mov    dx,600
    ret

init_routine    endp

;--------------------------------------------------------------------------
; Entry: AH=read page
;        AL=write page
;
; NOTE: This runs in protected mode!  Don't mess with the segment registers!
; This code must be relocatable and may not reference any data!
;
; Exit: VGA configured.
;       AX,BX,CX,DX,SI,DI may be trashed
;
; Derived from VGAKIT Version 3.4
;    Copyright 1988,89,90 John Bridges

    assume    ds:nothing, es:nothing

paging_routine    proc    far
    mov    ch,al
        mov     dx,3ceh        ;Enable extended registers
        mov     ax,200fh
        out     dx,ax
    mov    dl,0cch        ;bit 0
    in    al,dx
    mov    dl,0c2h
    and    al,11011111b
    shr    ch,1
    jnc    skpa
    or    al,00100000b
skpa:    out    dx,al
    mov    dl,0cfh        ;bits 1,2,3
    mov    al,0
    out    dx,al
    inc    dx
    in    al,dx
    dec    dx
    and    al,11111000b
    or    al,ch
    mov    ah,al
    mov    al,0
    out    dx,ax

    ret
paging_routine    endp

;--------------------------------------------------------------------------

cseg    ends
    end