8.3. Operations

8.3.1. Establishing an ISR

The rtems_interrupt_catch directive establishes an ISR for the system. The address of the ISR and its associated CPU vector number are specified to this directive. This directive installs the RTEMS interrupt wrapper in the processor’s Interrupt Vector Table and the address of the user’s ISR in the RTEMS’ Vector Table. This directive returns the previous contents of the specified vector in the RTEMS’ Vector Table.

8.3.2. Directives Allowed from an ISR

Using the interrupt manager ensures that RTEMS knows when a directive is being called from an ISR. The ISR may then use system calls to synchronize itself with an application task. The synchronization may involve messages, events or signals being passed by the ISR to the desired task. Directives invoked by an ISR must operate only on objects which reside on the local node. The following is a list of RTEMS system calls that may be made from an ISR:

• Task Management Although it is acceptable to operate on the RTEMS_SELF task (e.g. the currently executing task), while in an ISR, this will refer to the interrupted task. Most of the time, it is an application implementation error to use RTEMS_SELF from an ISR.

  • rtems_task_suspend

  • rtems_task_resume

• Interrupt Management

  • rtems_interrupt_enable

  • rtems_interrupt_disable

  • rtems_interrupt_flash

  • rtems_interrupt_lock_acquire

  • rtems_interrupt_lock_release

  • rtems_interrupt_lock_acquire_isr

  • rtems_interrupt_lock_release_isr

  • rtems_interrupt_is_in_progress

  • rtems_interrupt_catch

• Clock Management

  • rtems_clock_set

  • rtems_clock_get_tod

  • rtems_clock_get_tod_timeval

  • rtems_clock_get_seconds_since_epoch

  • rtems_clock_get_ticks_per_second

  • rtems_clock_get_ticks_since_boot

  • rtems_clock_get_uptime

• Timer Management

  • rtems_timer_cancel

  • rtems_timer_reset

  • rtems_timer_fire_after

  • rtems_timer_fire_when

  • rtems_timer_server_fire_after

  • rtems_timer_server_fire_when

• Event Management

  • rtems_event_send

  • rtems_event_system_send

  • rtems_event_transient_send

• Semaphore Management

  • rtems_semaphore_release

• Message Management

  • rtems_message_queue_broadcast

  • rtems_message_queue_send

  • rtems_message_queue_urgent

• Signal Management

  • rtems_signal_send

• Dual-Ported Memory Management

  • rtems_port_external_to_internal

  • rtems_port_internal_to_external

• IO Management The following services are safe to call from an ISR if and only if the device driver service invoked is also safe. The IO Manager itself is safe but the invoked driver entry point may or may not be.

  • rtems_io_initialize

  • rtems_io_open

  • rtems_io_close

  • rtems_io_read

  • rtems_io_write

  • rtems_io_control

• Fatal Error Management

  • rtems_fatal

  • rtems_fatal_error_occurred

• Multiprocessing

  • rtems_multiprocessing_announce