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+Ada95 Interrupt Support
+#######################
+
+Introduction
+============
+
+This chapter describes what is required to enable Ada interrupt
+and error exception handling when using GNAT over RTEMS.
+
+The GNAT Ada95 interrupt support RTEMS was developed by
+Jiri Gaisler <jgais@ws.estec.esa.nl> who also wrote this
+chapter.
+
+Mapping Interrupts to POSIX Signals
+===================================
+
+In Ada95, interrupts can be attached with the interrupt_attach pragma.
+For most systems, the gnat run-time will use POSIX signal to implement
+the interrupt handling, mapping one signal per interrupt. For interrupts
+to be propagated to the attached Ada handler, the corresponding signal
+must be raised when the interrupt occurs.
+
+The same mechanism is used to generate Ada error exceptions.
+Three error exceptions are defined: program, constraint and storage
+error. These are generated by raising the predefined signals: SIGILL,
+SIGFPE and SIGSEGV. These signals should be raised when a spurious
+or erroneous trap occurs.
+
+To enable gnat interrupt and error exception support for a particular
+BSP, the following has to be done:
+
+# Write an interrupt/trap handler that will raise the corresponding
+  signal depending on the interrupt/trap number.
+
+# Install the interrupt handler for all interrupts/traps that will be
+  handled by gnat (including spurious).
+
+# At startup, gnat calls ``__gnat_install_handler()``. The BSP
+  must provide this function which installs the interrupt/trap handlers.
+
+Which CPU-interrupt will generate which signal is implementation
+defined. There are 32 POSIX signals (1 - 32), and all except the
+three error signals (SIGILL, SIGFPE and SIGSEGV) can be used. I
+would suggest to use the upper 16 (17 - 32) which do not
+have an assigned POSIX name.
+
+Note that the pragma interrupt_attach will only bind a signal
+to a particular Ada handler - it will not unmask the
+interrupt or do any other things to enable it. This have to be
+done separately, typically by writing various device register.
+
+Example Ada95 Interrupt Program
+===============================
+
+An example program (``irq_test``) is included in the
+Ada examples package to show how interrupts can be handled
+in Ada95. Note that generation of the test interrupt
+(``irqforce.c``) is BSP specific and must be edited.
+
+NOTE: The ``irq_test`` example was written for the SPARC/ERC32
+BSP.
+
+Version Requirements
+====================
+
+With RTEMS 4.0, a patch was required to psignal.c in RTEMS
+sources (to correct a bug associated to the default action of
+signals 15-32).   The SPARC/ERC32 RTEMS BSP includes the``gnatsupp`` subdirectory that can be used as an example
+for other BSPs.
+
+With GNAT 3.11p, a patch is required for ``a-init.c`` to invoke
+the BSP specific routine that installs the exception handlers.
+
+.. COMMENT: COPYRIGHT (c) 1988-2008.
+
+.. COMMENT: On-Line Applications Research Corporation (OAR).
+
+.. COMMENT: All rights reserved.
+