Intel 21152 manual Interrupt Routing, Interrupt ORing

Interrupt Routing 3

This chapter describes the way in which interrupts are routed. This information is provided as a reference for designers.

Because a total of 16 interrupts are connected to the secondary bus PCI slots (INTA#, INTB#, INTC#, and INTD# for each slot) and only four interrupts are driven to the card edge, the 16 incoming interrupts must be combined. This ORing of interrupts is performed in accordance with the PCI-to-PCI Bridge Architecture Specification.

Table 3-1shows the ORing of interrupts.

Table 3-1.	Interrupt ORing
	Device Number	Interrupt Pin	Interrupt Pin
		on Device	on Board Connector
	4	INTA#	INTA#
		INTB#	INTB#
		INTC#	INTC#
		INTD#	INTD#
	5	INTA#	INTB#
		INTB#	INTC#
		INTC# I	INTD#
		INTD#	INTA#
	6	INTA#	INTC#
		INTB#	INTD#
		INTC#	INTA#
		INTD#	INTB#
	7	INTA#	INTD#
		INTB#	INTA#
		INTC#	INTB#
		INTD#	INTC#

In accordance with the PCI-to-PCI Bridge Architecture Specification, Revision 1.0, interrupts of the devices on the secondary slots are wire ORed and routed to PCI fingers of the EB152.

21152 PCI-to-PCI Bridge Evaluation Board User’s Guide 3-1