Int 13 Fn 20  U - Compaq, Atapi Removable Media Device - Get Current Medi  [b]

   AH = 20h
   DL = drive number (00h,01h)

Return: CF clear if successful
       AL = media type (see #0197)
       AH = 00h
   CF set on error
       AH = error code
       01h invalid request
       30h drive does not support media sense
       31h no such drive / media not present
       32h non-default media / drive does not supporte media type

Notes: this function is supported by the 3/8/93 ROM BIOS, but only partially
     (AL is always 00h when successful) by the 8/3/93 version
   this function is also supported by some recent versions of the Phoenix
     486 BIOS

(Table 0197)
Values for Compaq/ATAPI diskette media type:
 03h   720K  (1M unformatted)
 04h   1.44M (2M unformatted)
 06h   2.88M (4M unformatted)
 0Ch   360K
 0Dh   1.2M
 0Eh   Toshiba 3mode
 0Fh   NEC 3mode (1024-byte sectors)
 10h   ATAPI Removable Media Device