Interrupter And Interrupt Handler - Motorola MVME2600 Series Reference Manual

Universe (VMEbus to PCI) Chip

Interrupter and Interrupt Handler

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Interrupter
The Universe interrupt channel provides a flexible scheme to map
interrupts to either the PCI bus or VMEbus interface. Interrupts are
generated from either hardware or software sources (Refer to Interrupter
in the Universe User Manual for a full description of hardware and
software sources.). Interrupt sources can be mapped to any of the PCI bus
or VMEbus interrupt output pins. Interrupt sources mapped to VMEbus
interrupts are generated on the VMEbus interrupt output pins VIRQ#[7:1].
When a software and hardware source are assigned the same VIRQn# pin,
the software source always has higher priority.
Interrupt sources mapped to PCI bus interrupts are generated on one of the
INT#[7:0] pins. To be fully PCI compliant, all interrupt sources must be
routed to a single INT# pin.
For VMEbus interrupt outputs, the Universe interrupter supplies an 8-bit
STATUS/ID to a VMEbus interrupt handler during the IACK cycle, and
optionally generates an internal interrupt to signal that the interrupt vector
has been provided. (Refer to VMEbus Interrupt Generation in the Universe
User Manual.)
Interrupts mapped to PCI bus outputs are serviced by the PCI interrupt
controller. The CPU determines which interrupt sources are active by
reading an interrupt status register in the Universe. The source negates its
interrupt when it has been serviced by the CPU. (Refer to PCI Interrupt
Generation in the Universe User Manual.)
VMEbus Interrupt Handling
A VMEbus interrupt triggers the Universe io generate a normal VMEbus
IACK cycle and generate the specified interrupt output. When the IACK
cycle is complete, the Universe releases the VMEbus and the interrupt
vector is read by the PCI resource servicing the interrupt output. Software
interrupts are ROAK, while hardware, and internal interrupts are RORA.