109 lines
2.1 KiB
NASM
109 lines
2.1 KiB
NASM
title "Wd Hard.asm"
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;++
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;
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; Copyright (c) 1992 Microsoft Corporation
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; Copyright (c) 1993 Western Digital 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 implements the baning code for the WD90Cxx.
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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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; Author:
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;
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; Chung-I Chiang, Harold Huang Western Digital Corporation
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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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;---------------------------------------
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;
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; Western Digital banking control port.
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;
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SEGMENT_SELECT_PORT equ 03ceh ;banking control here
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SEQ_ADDRESS_PORT equ 03C4h ;Sequencer Address register
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WD_PR0A equ 09h
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WD_PR0B equ 0Ah
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IND_MEMORY_MODE equ 04h ;Memory Mode register index in Sequencer
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CHAIN4_MASK equ 08h ;Chain4 bit in Memory Mode register
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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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subttl "Bank Switching Stub"
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;
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; Bank switching code. This is a 1-64K-read/1-64K-write bank adapter
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; (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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align 4
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_BankSwitchStart proc ;start of bank switch code
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push ebx
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push eax
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push edx
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mov dx,SEGMENT_SELECT_PORT
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in al,dx
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mov ebx,eax ;must save 3CE current index
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pop edx
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pop eax
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push edx
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shl eax,12 ;read bank in PRO0A
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mov al,WD_PR0A
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mov dx,SEGMENT_SELECT_PORT
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out dx,ax
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pop edx
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mov eax,edx
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shl eax,12 ;write bank in PRO0B
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mov al,WD_PR0B
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mov dx,SEGMENT_SELECT_PORT
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out dx,ax
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mov eax,ebx ;restore 3CE index
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mov dx,SEGMENT_SELECT_PORT
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out dx,al
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pop ebx
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ret ; This should be a fatal error ...
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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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