INT 68 - APPC/PC - CONVERT
        AH = FBh
        DS:DX -> control block (see below)

Format of control block:
Offset  Size    Description
 00h 12 BYTEs   reserved
 0Ch    WORD    1A00h
 0Eh  6 BYTEs   0
 14h    DWORD   (high byte first) return code
 18h    BYTE    conversion
                   00h ASCII to EBCDIC
                   01h EBCDIC to ASCII
 19h    BYTE    character set
                   00h AE
                   01h A
                   02h G
 1Ah    WORD    length of string to convert
 1Ch    DWORD   pointer to source
 20h    DWORD   pointer to target