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1590

Category: BIOS

INT 15 - OS HOOK - DEVICE BUSY (AT,PS)

	AH = 90h
	AL = device type (see #00507)
	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: AH=91h,INT 13/AH=00h,INT 17/AH=00h,INT 1A/AH=83h


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