INT 21 - Advanced SCSI Programming Interface (ASPI) - INTERFACE
        AX = 4402h
        BX = file handle for device "SCSIMGR$"
        CX = 0004h
        DS:DX -> buffer for function address
Return: CF clear if successful
            AX = 0004h
        CF set on error
            AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:   the function address is called with the address of a SCSI Request
          Block on the stack and the caller must clean up the stack
SeeAlso: INT 11/AH=FFh"WD7000"

Format of SCSI Request Block (64 bytes):
Offset  Size    Description
 00h    BYTE    request number
                00h "HA_INQ"     host adapter inquiry
                01h "GET_TYPE"   get device type
                02h "EXEC_SIO"   execute SCSI I/O
                03h "ABORT_SRB"  abort SRB
                04h "RESET_DEV"  reset SCSI device
                05h "SET_HAPRMS" set host adapter parameters
 01h    BYTE    request status
                00h not done yet
                02h aborted
                04h SCSI I/O error
                80h invalid
                81h no adapter
                82h no device attached
                else status
 02h    BYTE    host adapter ID
 03h    BYTE    request flags
                bit 3: ???
 04h    DWORD   reserved
---request 00h---
 08h    BYTE    (returned) number of host adapters
 09h    BYTE    (returned) target adapter ID
 0Ah 16 BYTEs   (returned) manager ID
 1Ah 16 BYTEs   (returned) adapter ID
 2Ah 16 BYTEs   (returned) parameters
---request 01h---
 08h    BYTE    target ID
 09h    BYTE    logical unit number
 0Ah    BYTE    (returned) device type
                01h streamer
---request 02h---
 08h    BYTE    target ID
 09h    BYTE    logical unit number
 0Ah    DWORD   data allocation length
 0Eh    BYTE    sense allocation length
 0Fh    DWORD   data buffer pointer
 13h    DWORD   next request pointer (for linking)
 17h    BYTE    CDB length
 18h    BYTE    (returned) host adapter status
                11h select timeout
                12h data overrun
                13h bus error
                14h bus failure
 19h    BYTE    (returned) target status
                02h sense data stored in SRB
                08h target busy
                18h reservation error
 1Ah    DWORD   post routine address
 1Eh    WORD    real mode Post DS
 20h    DWORD   SRB pointer
 24h    WORD    reserved
 26h    DWORD   SRB physical address
 2Ah 22 BYTEs   SCSIMGR$ workspace
 40h  N BYTEs   CCB (20-24 bytes)
---request 04h---
 08h    BYTE    target ID
 09h    BYTE    logical unit number
 0Ah 14 BYTEs   reserved
 18h    BYTE    (returned) host adapter status (see above)
 19h    BYTE    (returned) target status (see above)
 1Ah    DWORD   post routine address
 1Eh 34 BYTEs   workspace

Format of CCB:
Offset  Size    Description
 00h    BYTE    command code
                01h rewind
                05h get block size limits
                08h read
                0Ah write
                10h write file marks
                11h SCSI Space (set position?)
                12h SCSI Inquire
                19h erase
                1Bh load/unload media
 01h    BYTE    flags
                bits 4-0: vary by function
                bits 7-5: logical unit number
 02h    BYTE    "adr_1"
 03h    BYTE    "adr_0"
 04h    BYTE    length
 05h    BYTE    control
        ...
 06h/0Ah 14 BYTEs buffer for sense data