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Table of Contents
7. PMODE/W MSDOS Extender
7.2. PMODE/W Supported DPMI INT 31h functions
7.2.24. Function 0303 - Allocate Real Mode Callback Address
7.2.24. Function 0303 - Allocate Real Mode
Callback Address
PMODE/W API
This function 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, TSR, etc... so that the real mode program can call
procedures within the protected mode program.
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 the callback routine.
Out:
if successful:
carry flag clear
CX:DX = segment:offset of real mode callback
if failed:
carry flag set
Notes:
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
release a callback that it is no longer using.
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