INT 15 - OS HOOK - DEVICE BUSY (AT,PS)
AH = 90h
AL = device type
00h disk
01h diskette
02h keyboard
03h PS/2 pointing device
21h waiting for keyboard input (Phoenix BIOS)
80h network
FBh digital sound (Tandy)
FCh disk reset (PS)
FDh diskette motor start
FEh printer
ES:BX -> request block for type codes 80h through BFh
CF clear
Return: CF set if wait time satisfied
CF clear if driver must perform wait
AH = 00h
Notes:  type codes are allocated as follows:
00-7F non-reentrant devices; OS must arbitrate access
80-BF reentrant devices; ES:BX points to a unique control block
C0-FF wait-only calls, no complementary INT 15/AH=91h call
floppy and hard disk BIOS code uses this call to implement a timeout;
for device types 00h and 01h, a return of CF set means that the
timeout expired before the disk responded.
this function should be hooked by a multitasker to allow other tasks
to execute while the BIOS is waiting for I/O completion; the default
handler merely returns with AH=00h and CF clear
SeeAlso: INT 13/AH=00h,INT 17/AH=00h,INT 1A/AH=83h

See also: 1591

1590 - OS HOOK - DEVICE BUSY (AT,PS)