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Raven PCI Bridge ASIC

interrupt source was the 8259, the interrupt handler issues an EOI request to the RavenMPIC. This resets the In-Service bit for the 8259 within the RavenMPIC and allows it to recognize higher- priority interrupt requests, if any, from the 8259. If none of the nested interrupt modes of the 8259 are enabled, the interrupt handler issues an EOI request to the 8259.

a.The device driver interrupt service routine associated with this interrupt vector is invoked.

b.If the interrupt source was not the 8259, the interrupt handler issues an EOI request for this interrupt vector to the RavenMPIC. If the interrupt source was the 8259 and any of the nested interrupt modes of the 8259 are enabled, the interrupt handler issues an EOI request to the 8259.

Normally, interrupts from ISA devices are connected to the 8259 interrupt controller. ISA devices typically rely on the 8259 Interrupt Acknowledge to flush buffers between the ISA device and system memory. If interrupts from ISA devices are directly connected to the RavenMPIC (bypassing the 8259), the device driver interrupt service routine must read status from the ISA device to ensure buffers between the device and system memory are flushed.

Reset State

After a power-on reset, the RavenMPIC state is as follows:

Current task priority for all CPUs set to 15.

All interrupt source priorities set to 0.

All interrupt source mask bits set to 1.

All interrupt source activity bits cleared.

Processor Init register cleared.

All counters stopped and interrupts disabled.

Controller mode set to 8259 pass-through.

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Computer Group Literature Center Web Site

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Motorola MVME2300 Series manual Reset State