
Raven Interrupt Controller Implementation
http://www.motorola.com/computer/literature
2-51
2
❏
Base Count Register
❏
Vector-Priority Register
❏
Destination Register
Interrupt Delivery Modes
The direct and distributed interrupt delivery modes are supported.
Note
The direct deliver mode has sub modes of multicast or non-
multicast. The Interprocessor Interrupts (IPIs) and Timer
interrupts operate in the direct delivery mode. The externally
sourced or I/O interrupts operate in the distributed mode.
In the direct delivery mode, the interrupt is directed to one or both
processors. If it is directed to two processors (that is, multicast), it will be
delivered to two processors. The interrupt is delivered to the processor
when the priority of the interrupt is greater than the priority contained in
the task register for that processor, and when the priority of the interrupt is
greater than any interrupt which is in-service for that processor. An
interrupt is considered to be in service from the time its vector is returned
during an interrupt acknowledge cycle until an EOI is received for that
interrupt. The EOI cycle indicates the end of processing for the highest
priority in- service interrupt.
In the distributed delivery mode, the interrupt is pointed to one or more
processors but it will be delivered to only one processor. Therefore, for
externally sourced or I/O interrupts, multicast delivery is not
supported.The interrupt is delivered to a processor when the priority of the
interrupt is greater than the priority contained in the task register for that
processor, and when the priority of the interrupt is greater than any
interrupt which is in-service for that processor, and when the priority of
that interrupt is the highest of all interrupts pending for that processor, and
when that interrupt is not in-service for the other processor. If both
destination bits are set for each processor, the interrupt will be delivered to
the processor that has a lower task register priority.