Int 21 Fn 4405  - DOS 2+ - Ioctl - Write To Block Device Control Channel   [D]

   AX = 4405h
   BL = drive number (00h = default, 01h = A:, etc)
   CX = number of bytes to write
   DS:DX -> data to write

Return: CF clear if successful
       AX = number of bytes actually written
   CF set on error
       AX = error code (01h,05h,06h,0Dh) (see AH=59h)

Note:  format of data is driver-specific

See Also: AX=4403h,AX=4404h,INT 2F/AX=122Bh