RTEMS Hewlett Packard PA-RISC Applications Supplement
In addition to the thirty-two unique interrupt sources supported by the PA-RISC architecture, RTEMS also supports the installation of handlers for each of the thirty-two external interrupts supported by the PA-RISC architecture. Except for interrupt vector 4, each of the interrupt vectors 0 through 31 may be associated with a user-provided interrupt handler. Interrupt vector 4 is used for external interrupts. When an external interrupt occurs, the RTEMS external interrupt handler is invoked and the actual interrupt source is indicated by status bits in the EIR (External Interrupt Request) register. The RTEMS external interrupt handler (or interrupt vector four) examines the EIR to determine which interrupt source requires servicing.
RTEMS supports sixty-four interrupt vectors for the PA-RISC. Vectors 0 through 31 map to the normal interrupt sources while RTEMS interrupt vectors 32 through 63 are directly associated with the external interrupt sources indicated by bits 0 through 31 in the EIR.
The exact set of interrupt sources which are checked for by the RTEMS external interrupt handler and the order in which they are checked are configured by the user in the CPU Configuration Table. If an external interrupt occurs which does not have a handler configured, then the spurious interrupt handler will be invoked. The spurious interrupt handler may also be specifiec by the user in the CPU Configuration Table.
RTEMS Hewlett Packard PA-RISC Applications Supplement
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