Raven Interrupt Controller Implementation
2-53
2
modes of activation; low level or active high positive edge. External
interrupt 0 can be either level or edge activated with either polarity. The
Interprocessor and timers interrupts are event activated.
CSR’s Readability
Unless explicitly specified, all registers are readable and return the last
value written. The exceptions are the IPI dispatch registers and the EOI
registers which return zeros on reads, the interrupt source ACT bit which
returns current interrupt source status, the interrupt acknowledge register
which returns the vector of the highest priority interrupt which is currently
pending, and reserved bits which returns zeros. The interrupt acknowledge
register is also the only register which exhibits any read side-effects.
Interrupt Source Priority
Each interrupt source is assigned a priority value in the range from 0 to 15
where 15 is the highest. In order for delivery of an interrupt to take place
the priority of the source must be greater than that of the destination
processor. Therefore setting a source priority to zero inhibits that interrupt.
Processor’s Current Task Priority
Each processor has a task priority register which is set by system software
to indicate the relative importance of the task running on that processor.
The processor will not receive interrupts with a priority level equal to or
lower than its current task priority. Therefore setting the current task
priority to 15 prohibits the delivery of all interrupts to the associated
processor.
Nesting of Interrupt Events
A processor is guaranteed never to have an in-service interrupt preempted
by an equal or lower priority source. 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.
Summary of Contents for MVME2700 Series
Page 1: ...MVME2600 2700 Series Single Board Computer Programmer s Reference Guide V2600A PG2 ...
Page 13: ...xiv ...
Page 15: ...xvi ...
Page 67: ...1 50 Board Description and Memory Maps 1 ...
Page 151: ...2 84 Raven PCI Host Bridge Multi Processor Interrupt Controller Chip 2 ...
Page 215: ...3 64 Falcon ECC Memory Controller Chip Set 3 ...
Page 277: ...Glossary GL 14 G L O S S A R Y ...