INT 21 - Phar Lap 386/DOS-Extender - CALL REAL-MODE PROCEDURE, REGISTERS
AX = 2510h
EBX = CS:IP of real-mode procedure to call
ECX = number of two-byte words to copy to protected-mode stack to
real-mode stack
DS:EDX -> pointer to parameter block (see below)
Return: CF clear if successful
all segment registers unchanged,
EDX unchanged
all other general registers contain values set by real-mode proc
all other flags are set as they were left by real-mode procedure
real-mode register values are returned in the parameter block
CF set on error
EAX = error code
01h not enough real-mode stack space
Note:   unlike most of the preceding 25xxh functions, this one is not
supported by FlashTek X-32VM
SeeAlso: AX=250Fh

Format of parameter block:
Offset  Size    Description
00h    WORD    real-mode DS value
02h    WORD    real-mode ES value
04h    WORD    real-mode FS value
06h    WORD    real-mode GS value
08h    DWORD   real-mode EAX value
0Ch    DWORD   real-mode EBX value
10h    DWORD   real-mode ECX value
14h    DWORD   real-mode EDX value

See also: 21250E

212510 - Phar Lap 386/DOS-Extender - CALL REAL-MODE PROCEDURE, REGISTERS