RBIL61 - INT 13 - FLOPPY DISK - DETECT DISK CHANGE (XT 1986/1/10 or later,XT286,AT,PS)

INT 13 - FLOPPY DISK - DETECT DISK CHANGE (XTIBM PC XT 1986/1/10 or later,XT286IBM PC XT/286,ATIBM PC AT,PSIBM PS/2, any model)
	AH = 16h
	DL = drive number (00h-7Fh)
	SI = 0000h (to avoid crash on AT&TAmerican Telephone and Telegraph 6300)
Return: CF clear if change line inactive
	    AH = 00h (disk not changed)
	CF set if change line active
	    AH = status
		01h invalid command (SyQuest)
		06h change line active or not supported
		80h drive not ready or not present
Notes:	call AH=15h first to determine whether the drive supports a change
	  line
	this call also clears the media-change status, so that a disk change
	  is only reported once
BUGS:	some versions of Award 386 Modular BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. and AMIAmerican Megatrends, Inc.(American Megatrends, Inc.) A hardware, software and firmware company founded in 1985. BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. fail to clear
	  the media-change status
	AT&TAmerican Telephone and Telegraph 6300 WGS systems crash if SI <> 0 on entry.
	some pre 1986/08/04 Compaq ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. have a serious bug where this
	  function may re-configure a hard disk depending on what is located
	  at ES:[BX] and data indexed to by it. MS-DOS/PCIBM PC DOS IO.SYS/IBMBIO.COM
	  install a special filter when they detect Compaq ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. BIOSes with
	  earlier dates.
	some Compaq 286 systems have a bug in all INT 13h functions >= 16h,
	  which causes the byte at DS:0074h to be destroyed when called for
	  hard disks (DL >= 80h). MS-DOS/PCIBM PC DOS IO.SYS/IBMBIO.COM performs a
	  test on this bug using this sub-function, and if found installs a
	  special filter which points DS into ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs., so that it cannot cause
	  any harm.
	some drives (or controllers???) forget the change line status
	  if another drive is accessed afterwards. The DOS BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. takes care
	  of this by not relying on the reported change line status when
	  the change line is not active and a different drive is accessed,
	  instead it reports "don't know" to the DOS kernel.
SeeAlso: AH=15h,AH=49h