ABOUT ext int 13

我用ah=42h读物理盘，参数已经设置好，但dpmi调用ext int 13不成功或死机，下面是ext int 13 和我对相应参数的设置,是否有错误？谢谢！
INT 13 - IBM/MS INT 13 Extensions - EXTENDED READ
    AH = 42h
    DL = drive number
    DS:SI -> disk address packet (see #00272)
Return: CF clear if successful
    AH = 00h
    CF set on error
    AH = error code (see #00234)
    disk address packet\'s block count field set to number of blocks
    successfully transferred
Format of disk address packet:
Offset    Size    Description    (Table 00272)
00h    BYTE    10h (size of packet)
01h    BYTE    reserved (0)
02h    WORD    number of blocks to transfer (max 007Fh for Phoenix EDD)
04h    DWORD    -> transfer buffer
08h    QWORD    starting absolute block number
        (for non-LBA devices, compute as
        (Cylinder*NumHeads + SelectedHead) * SectorPerTrack +
        SelectedSector - 1
我定义结构体
typedef struct i13ap
{
   BYTE sizeofpacket;
   BYTE reserved;
   WORD numberofblocks;
   DWORD transfer_buffer;
   DWORD LOLBA;
   DWORD HILBA;
}INT13AP;
INT13AP INT13;
INT13.transfer_buffer=(DWORD)lpBuffer;
将该结构体的地址付给ds:si
   callStruct.esi = LOWORD(&INT13);    // Offset of struct buffer
   callStruct.ds  = HIWORD(&INT13);    // Segment of struct
buffer
多谢指点！

我猜你错误的原因可能是参数包的内容设置不正确，特别是第一字节的大小域，必须设置为0x10h
typedef struct i13ap
{
   BYTE sizeofpacket;
   BYTE reserved;
   WORD numberofblocks;
   DWORD transfer_buffer;
   DWORD LOLBA;
   DWORD HILBA;
}INT13AP;
INT13AP INT13;
INT13.sizeofpacket=0x10;
INT13.sizeofpacket=0x0;
INT13.numberofblocks=??;
INT13.transfer_buffer=(DWORD)lpBuffer;

//下面的DS：SI的赋值是否正确还看看你的callStruc.si
//这里的DS：SI应该赋给伪变量_DS，_SI

将该结构体的地址付给ds:si
   callStruct.si = LOWORD(&INT13);    // Offset of struct buffer
   callStruct.ds  = HIWORD(&INT13);    // Segment of struct
buffer