pmodew.doc

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  Allocates a block of extended memory.

In:
  AX     = 0501h
  BX:CX  = size of block in bytes (must be non-zero)

Out:
  if successful:
    carry flag clear
    BX:CX  = linear address of allocated memory block
    SI:DI  = memory block handle (used to resize and free block)

  if failed:
    carry flag set

Notes:
) The allocated block is guaranteed to have at least dword alignment.

) This function does not allocate any descriptors for the memory block. It is
  the responsibility of the client to allocate and initialize any descriptors
  needed to access the memory with additional function calls.

2.30 - Function 0502h - Free Memory Block:
------------------------------------------

  Frees a memory block previously allocated with the Allocate Memory Block
function (0501h).

In:
  AX     = 0502h
  SI:DI  = memory block handle

Out:
  if successful:
    carry flag clear

  if failed:
    carry flag set

Notes:
) No descriptors are freed by this call. It is the client's responsibility to
  free any descriptors that it previously allocated to map the memory block.
  Descriptors should be freed before memory blocks.

2.31 - Function 0503h - Resize Memory Block:
--------------------------------------------

  Changes the size of a memory block previously allocated with the Allocate
Memory Block function (0501h).

In:
  AX     = 0503h
  BX:CX  = new size of block in bytes (must be non-zero)
  SI:DI  = memory block handle

Out:
  if successful:
    carry flag clear
    BX:CX  = new linear address of memory block
    SI:DI  = new memory block handle

  if failed:
    carry flag set

Notes:
) After this function returns successfully, the previous handle for the memory
  block is invalid and should not be used anymore.

) It is the client's responsibility to update any descriptors that map the
  memory block with the new linear address after resizing the block.

2.32 - Function 0800h - Physical Address Mapping:
-------------------------------------------------

  Converts a physical address into a linear address. This functions allows the
client to access devices mapped at a specific physical memory address.
Examples of this are the frame buffers of certain video cards in extended
memory.

In:
  AX     = 0800h
  BX:CX  = physical address of memory
  SI:DI  = size of region to map in bytes

Out:
  if successful:
    carry flag clear
    BX:CX  = linear address that can be used to access the physical memory

  if failed:
    carry flag set

Notes:
) It is the caller's responsibility to allocate and initialize a descriptor
  for access to the memory.

) Clients should not use this function to access memory below the 1 MB
  boundary.

2.33 - Function 0801h - Free Physical Address Mapping:
------------------------------------------------------

  Releases a mapping of physical to linear addresses that was previously
obtained with function 0800h.

In:
  AX     = 0801h
  BX:CX  = linear address returned by physical address mapping call

Out:
  if successful:
    carry flag clear

  if failed:
    carry flag set

Notes:
) The client should call this function when it is finished using a device
  previously mapped to linear addresses with function 0801h.

2.34 - Function 0900h - Get and Disable Virtual Interrupt State:
----------------------------------------------------------------

  Disables the virtual interrupt flag and returns the previous state of it.

In:
  AX     = 0900h

Out:
  always successful:
    carry flag clear
    AL	   = 0 if virtual interrupts were previously disabled
    AL	   = 1 if virtual interrupts were previously enabled

Notes:
) AH is not changed by this function. Therefore the previous state can be
  restored by simply executing another INT 31h.

) A client that does not need to know the prior interrupt state can execute
  the CLI instruction rather than calling this function. The instruction may
  be trapped by a DPMI host and should be assumed to be very slow.

2.35 - Function 0901h - Get and Enable Virtual Interrupt State:
---------------------------------------------------------------

  Enables the virtual interrupt flag and returns the previous state of it.

In:
  AX     = 0901h

Out:
  always successful:
    carry flag clear
    AL	   = 0 if virtual interrupts were previously disabled
    AL	   = 1 if virtual interrupts were previously enabled

Notes:
) AH is not changed by this function. Therefore the previous state can be
  retstored by simply executing another INT 31h.

) A client that does not need to know the prior interrupt state can execute
  the STI instruction rather than calling this function. The instruction may
  be trapped by a DPMI host and should be assumed to be very slow.

2.36 - Function 0902h - Get Virtual Interrupt State:
----------------------------------------------------

  Returns the current state of the virtual interrupt flag.

In:
  AX     = 0902h

Out:
  always successful:
    carry flag clear
    AL	   = 0 if virtual interrupts are disabled
    AL	   = 1 if virtual interrupts are enabled

Notes:
) This function should be used in preference to the PUSHF instruction to
  examine the interrupt flag, because the PUSHF instruction returns the
  physical interrupt flag rather than the virtualized interrupt flag. On some
  DPMI hosts, the physical interrupt flag will always be enabled, even when
  the hardware interrupts are not being passed through to the client.

2.37 - Function EEFFh - Get DOS Extender Information:
-----------------------------------------------------

  Returns information about the DOS extender.

In:
  AX     = EEFFh

Out:
  if successful:
    carry flag clear
    EAX    = 'PMDW' (504D4457h)
    ES:EBX = selector:offset of ASCIIZ copyright string
    CH     = protected mode system type (0=raw, 1=XMS, 2=VCPI, 3=DPMI)
    CL     = processor type (3=386, 4=486, 5=586)
    DH     = extender MAJOR version (binary)
    DL     = extender MINOR version (binary)

  if failed:
    carry flag set

Notes:
) In PMODE/W's implementation of this function, the value returned in ES is
  equivalent to the 4G data selector returned in DS at startup.

) This function is always successful under PMODE/W.

------------------------------------------------------------------------------
-------------- 3 - Supported DOS extended INT 21h functions ------------------
------------------------------------------------------------------------------

  For the most part, PMODE/W extends only the most widely used DOS functions.
The term "extend" means to extend real mode 16:16 pointers which have a limit
of 1MB into the full protected mode range of 16:32 pointers with a range of
4GB. Since DOS can only address memory under 1MB, we must buffer any data that
is to be passed to or from DOS in low memory. Only DOS functions which use
16:16 pointers or segment registers need to be extended. This means that DOS
functions that are not listed here can still be used provided they don't make
use of those kinds of parameters. Examples of such functions are INT 21h
AH=30h or INT 21h AH=2, etc. The following is a detailed list of all functions
extended by PMODE/W. All segment registers used as parameters must be valid
protected mode selectors. Any functions that are not listed here will be
passed on to the real mode INT 21h handler without any buffering or
modification. This and the other sections on interrupts are provided as
reference as to how PMODE/W deals with these interrupts. It is assumed the
reader is familiar with the normal real mode operation of these functions.

3.0 - Function 09h - Write String to Standard Output:
-----------------------------------------------------

In:
  AH     = 09h
  DS:EDX -> '$' terminated string to write

Out:
  always successful

3.1 - Function 1Ah - Set Disk Transfer Area:
--------------------------------------------

In:
  AH	 = 1Ah
  DS:EDX -> buffer for DTA

Out:
  always successful

Notes:
) PMODE/W keeps an internal DTA buffer in low memory that is used to buffer
  any functions which use the DTA. After calling the real mode DOS function,
  the data will be transfered into the buffer specified by DS:EDX.

3.2 - Function 1Bh - Get Allocation Information for Default Drive:
------------------------------------------------------------------

In:
  AH     = 1Bh

Out:
  always successful:
    AL     = sectors per cluster
    ECX    = bytes per sector
    EDX    = total number of clusters
    DS:EBX -> media ID byte

Notes:
) This functions simply converts the real mode segment:offset returned by DOS
  to a protected mode selector:offset.

3.3 - Function 1Ch - Get Allocation Information for Specific Drive:
-------------------------------------------------------------------

In:
  AH     = 1Ch
  DL     = drive number

Out:
  if successful:
    AL     = sectors per cluster
    ECX    = bytes per sector
    EDX    = total number of clusters
    DS:EBX -> media ID byte

  if failed:
    AL     = FFh (invalid drive)

Notes:
) This functions simply converts the real mode segment:offset returned by DOS
  to a protected mode selector:offset.

3.4 - Function 1Fh - Get Drive Parameter Block for Default Drive:
-----------------------------------------------------------------

In:
  AH     = 1Fh

Out:
  if successful:
    AL     = 0
    DS:EBX -> drive parameter block

  if failed:
    AL     = FFh (invalid drive)

Notes:
) This functions simply converts the real mode segment:offset returned by DOS
  to a protected mode selector:offset.

3.5 - Function 25h - Set Interrupt Vector:
------------------------------------------

In:
  AH	 = 25h
  AL	 = interrupt number
  DS:EDX -> interrupt routine

Out:
  if successful:
    carry flag clear

  if failed:
    carry flag set

Notes:
) This function is equivalent to INT 31h function 0205h.

3.6 - Function 2Fh - Get Disk Transfer Area:
--------------------------------------------

In:
  AH	 = 2Fh

Out:
  al