MVME5100 Single Board Computer Programmer's Reference Guide

2
Hawk PCI Host Bridge & Multi-Processor Interrupt Controller
Operation
Interprocessor Interrupts
Four interprocessor interrupt (IPI) channels are provided for use by all
processors. During system initialization the IPI vector/priority registers for
each channel should be programmed to set the priority and vector returned
for each IPI event. During system operation a processor may generate an
IPI by writing a destination mask to one of the IPI dispatch registers. Note
that each IPI dispatch register is shared by both processors. Each IPI
dispatch register has two addresses but they are shared by both processors.
That is there is a total of four IPI dispatch registers in the MPIC.
The IPI mechanism may be used for self interrupts by programming the
dispatch register with the bit mask for the originating processor.
Dynamically Changing I/O Interrupt Configuration
The interrupt controller provides a mechanism for safely changing the
vector, priority, or destination of I/O interrupt sources. This is provided to
support systems which allow dynamic configuration of I/O devices. In
order to change the vector, priority, or destination of an active interrupt
source, the following sequence should be performed:
❏ Mask the source using the MASK bit in the vector/priority register.
❏ Wait for the activity bit (ACT) for that source to be cleared.
❏ Make the desired changes.
❏ Unmask the source.
This sequence ensures that the vector, priority, destination, and mask
information remain valid until all processing of pending interrupts is
complete.
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