Intel 80286, 80287 manual Shutdown

	ADVANCED TOPICS
	Table 11-1. NPX Context Switching
Step	Operation
1.	Save the working registers
2.	Set up address for kernel work area
3.	Get current task 10 from Task Register
4.	Clear Task Switch flag to allow NPX work
5.	Inhibit interrupts
6.	Compare owner with current task 10
If same owner:
7a.	Restore working registers
7b.	and return
If owner is not
current task:	Use owner 10 to save old context in Its TSS
8a.
8b.	R,estore context of current task;
	restore working registers;
	and return

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(Figure 11-3)

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updated by a re-entrant procedure that is invoked by an inter-processor interrupt. The handler must ensure that the segment registers, the LDTR and the TR, are re-loaded. This happens automatically if the interrupt is serviced by a task switch.

11.6 SHUTDOWN

Shutdown occurs when a severe error condition prevents further processing. Shutdown is very similar to HLT in that the 80286 stops executing instructions. The 80286 externally signals shutdown as a Halt bus cycle with Al =0. The NMI or RESET input will force the 80286 out of shutdown. The INTR input is ignored during shutdown.

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