DOS/32 Advanced DOS Extender
- Programmer's Reference
2.26 - DPMI function 0303h
- Allocate Real Mode Callback Address
Returns a unique real
mode segment:offset, known as a "real mode callback" that will
transfer control from real mode to a protected mode procedure. Callback
addresses obtained with this function can be passed by a protected mode
program to a real mode application, interrupt handler, device driver, or
TSR, so that the real mode program can call procedures within the protected
mode program or notify the protected mode program of an event.
In: |
AX = 0303h
DS:ESI = selector:offset of protected mode procedure to call
ES:EDI = selector:offset of 32h-byte buffer for real mode register
data structure to be used when calling callback routine. |
Out: |
if successful:
CF clear
CX:DX = segment:offset of real mode callback
if failed:
CF set
AX = error code
8015h - callback unavailable
|
Notes:
a) A descriptor may be
allocated for each callback to hold the real mode SS descriptor. Real mode
callbacks are a limited system resource. A client should use the Free Real
Mode Callback Address DPMI function 0304h to release a callback that it
is no longer using.
b) The contents of the
real mode register data structure is not valid after the function call,
but only at the time of the actual callback.
Copyright © DOS/32 Advanced Team 1996-2002 All Rights Reserved
|