92 lines
1.7 KiB
NASM
92 lines
1.7 KiB
NASM
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title "Vga Hard.asm"
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;++
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;
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; Copyright (c) 1992 Microsoft Corporation
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;
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; Module Name:
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;
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; vgahard.asm
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;
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; Abstract:
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;
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; This module includes the banking stub.
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;
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; Environment:
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;
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; Kernel mode only.
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;
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; Revision History:
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;
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;
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;--
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.386p
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.xlist
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include callconv.inc ; calling convention macros
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.list
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_TEXT SEGMENT DWORD PUBLIC 'CODE'
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ASSUME DS:FLAT, ES:FLAT, SS:NOTHING, FS:NOTHING, GS:NOTHING
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page ,132
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;
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; Trident TVGA Bank switching code.
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; This is a 1-64K-read/1-64K-write bank adapter (VideoBanked1R1W).
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;
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; Input:
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; EAX = desired read bank mapping
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; EDX = desired write bank mapping
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;
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; Note: values must be correct, with no stray bits set; no error
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; checking is performed.
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;
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public _BankSwitchStart
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public _BankSwitchEnd
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_BankSwitchStart proc ;start of bank switch code
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push dx
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mov dx, 3CEh ; read bank
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mov ah, al
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xor ah, 2
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in al, dx
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push ax
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mov al, 0Eh
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out dx, ax
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pop ax
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out dx, al
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pop ax
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mov dx, 3C4h ; write bank
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mov ah, al
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xor ah, 2
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in al, dx ; save 3C4 index
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push ax
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mov al, 0Eh
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out dx, ax
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pop ax
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out dx, al
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ret
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if 0 ; 1RW
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mov ah, dl
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mov dx, 3C4h
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in al, dx
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push ax
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xor ah, 2
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mov al, 0Eh
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out dx, ax
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pop ax
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out dx, al
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ret
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endif
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_BankSwitchEnd:
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_BankSwitchStart endp
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_TEXT ends
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end
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