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262 lines
5.5 KiB
ArmAsm
262 lines
5.5 KiB
ArmAsm
! Copyright (c) 1997 Helmut Wirth <hfwirth@ping.at>
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! All rights reserved.
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!
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! Redistribution and use in source and binary forms, with or without
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! modification, are permitted provided that the following conditions
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! are met:
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! 1. Redistributions of source code must retain the above copyright
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! notice immediately at the beginning of the file, witout modification,
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! this list of conditions, and the following disclaimer.
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! 2. Redistributions in binary form must reproduce the above copyright
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! notice, this list of conditions and the following disclaimer in the
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! documentation and/or other materials provided with the distribution.
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! 3. The name of the author may not be used to endorse or promote products
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! derived from this software without specific prior written permission.
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!
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! THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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! IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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! OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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! IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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! INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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! NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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! DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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! THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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! (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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! THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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!
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! $FreeBSD$
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!
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! This driver is needed for Expanded Memory emulation (EMS). A driver
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! is needed here, because EMS drivers are installed as DOS devices
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! with the name "EMMXXXX0" and programs look for such a device while
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! checking the existence of EMS.
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! The driver is installed by CONFIG.SYS, it has no options. It uses
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! the emulator callback interrupt 0xff to initialize the EMS subsystem.
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! If EMS is not configured or if there is an error inside the emulator
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! the driver reports failure and does not install itself.
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! If all works, the driver changes the interrupt vector for int 0x67 to
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! point at itself. The resident part of the drivers simlpy routes calls
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! to int 0x67 to the correct subfunction of the emulator callback interrupt.
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use16
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.text
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.bss
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.data
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.align 0
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.org 0
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NumFunc = 15
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! Emulator interrupt entry
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EmulatorINT = 0xFF
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! Emulator EMS callback function
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EMU_EMS = 0x2
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EMU_EMS_CTL = 0
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EMU_EMS_CALL = 1
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! DOS print message
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DOSMesg = 0x9
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cr = 0xd
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lf = 0xa
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eom = '$' ! DOS end of string
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EMSintnum = 0x67
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Intoffset = (EMSintnum * 4)
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.globl _main
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_main:
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driverhead:
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.long -1 ! link to next device driver
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.word 0xC000 ! attribute word for driver
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.word Strategy ! ptr to strategy routine
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.word Interrupt ! ptr to interrupt service routine
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.ascii "EMMXXXX0" ! logical device name
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reqhead:
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.long 0
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vectordone:
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.word 0 ! != 0 , if vector installed
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FuncTable:
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.word InitDrv ! initialize driver
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.word Noop ! media Check
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.word Noop ! build BPB
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.word Noop ! Ioctl
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.word Noop ! read
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.word Noop ! non destructive read
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.word Noop ! input status
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.word Noop ! flush input
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.word Noop ! write
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.word Noop ! write with verify
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.word Noop ! output status
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.word Noop ! flush output
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.word Noop ! ioctl output
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.word Noop ! open device
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.word Noop ! close device
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.word Noop ! removeable media check
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Strategy:
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seg cs
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mov [reqhead], bx
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seg cs
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mov [reqhead+2],es
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retf
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Interrupt:
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push ax
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push bx
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push cx
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push dx
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push ds
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push es
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push di
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push si
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push bp
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push cs
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pop ds
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les di,[reqhead] ! load pointer to request header
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seg es
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movb bl,[di+2]
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xorb bh,bh
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cmp bx, #NumFunc
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jle dointr
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call errorhandler
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jmp intrend
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dointr:
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shl bx,#1
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call [bx+FuncTable]
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les di,[reqhead] ! load pointer to request header
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intrend:
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or ax,#0x100 ! done bit
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seg es
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mov [di+3],ax
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pop bp
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pop si
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pop di
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pop es
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pop ds
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pop dx
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pop cx
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pop bx
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pop ax
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retf
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errorhandler:
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mov ax,#0x8003 ! report error to caller
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ret
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! This is done for all functions except init. It supports the different
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! methods for an EMS installation check described in the LIM EMS 4.0 spec
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Noop:
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call installvector
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xor ax,ax
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ret
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! The interrupt vector installed for int 0x67 points to this routine
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intr67:
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push ax ! Save original AX
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mov ah, #EMU_EMS ! Emuint function
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mov al, #EMU_EMS_CALL ! Emuint subfunction
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int EmulatorINT ! Call emulator for EMS
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iret
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installvector:
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push cs
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pop ds ! load DS to use local data
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mov ax,[vectordone]
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cmp ax,#0
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jne isinstalled ! already installed
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push di ! save request header pointer
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push es
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mov ax, #0 ! write the new interrupt vector
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mov es, ax
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mov di, #Intoffset
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seg es
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mov [di], #intr67
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seg es
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mov [di+2], cs
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pop es
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pop di
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mov ax,#1
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mov [vectordone],ax
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isinstalled:
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ret
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InitDrv:
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push cs
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pop ds
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push ax
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mov ah, #EMU_EMS ! Emuint function
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mov al, #EMU_EMS_CTL ! Emuint subfunction
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int EmulatorINT
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cmp ax,#0 ! check if successful
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je Fail
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call installvector
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push cs
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pop ds
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mov ah, #DOSMesg
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mov dx, #Success
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int 0x21
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seg es
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mov [di+14], #InitDrv ! address break for driver
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seg es
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mov [di+16], cs
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xor ax,ax
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ret
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Fail:
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push cs
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pop ds
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mov ah, #DOSMesg
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mov dx, #Failure
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int 0x21
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seg es
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movb [di+13],#0
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seg es
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mov [di+20],cs
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seg es
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mov [di+14],#0 ! address break == 0, no driver
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seg es
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mov [di+16],cs
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ret
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Success:
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.ascii "Doscmd EMS 4.0 driver installed"
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.byte cr,lf,eom
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Failure:
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.byte cr,lf,lf
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.ascii "EMS emulation is disabled"
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.byte cr,lf
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.ascii "Driver not installed"
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.byte cr,lf,lf,eom
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end
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