MVME5100 Single Board Computer Programmer's Reference Guide

Reset State
Multi-Processor Interrupt Controller (MPIC)
– The device driver interrupt service routine associated with this
interrupt vector is invoked.
– If the interrupt source was not the 8259, the interrupt handler
issues an EOI request for this interrupt vector to the MPIC. 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 MPIC (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.
After power on reset, the MPIC state is:
❏ Current task priority for all CPUs set to 15.
❏ All interrupt source priorities set to zero.
❏ All interrupt source mask bits set to a one.
❏ All interrupt source activity bits cleared.
❏ Processor Init Register is cleared.
❏ All counters stopped and interrupts disabled.
❏ Controller mode set to 8259 pass-through.
http://www.motorola.com/computer/literature 2-63
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