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Lucas Digital Engine Control Unit

Mission-critical Ada 95 for Motorola M68000 family targets

Credit: Lucas Aerospace

Note: The HOLD III Ada compiler is superseded by M68K Ada.

The HOLD III Ada 95 compiler was developed for the High Order Language Demonstration (HOLD) program run by Lucas Aerospace and part funded by the UK Ministry of Defence. It is based on the GNU C compiler from the Free Software Foundation and includes the validated GNAT Ada 95 front end from New York University.

The application domain is safety-critical embedded computers such as the Lucas Full Authority Digital Engine Controller (FADEC) used on Rolls Royce RB199 engines. This is the first time that a GCC-based Ada compiler has been used for embedded applications that require such a high level of correctness, and the HOLD III program has been an ideal way of demonstrating that this can be done.

Being delivered in November 1996, HOLD III Ada 95 was also the first Ada 95 compiler for the Motorola M68000 family,  and continues to be the only compiler targeted to the 68020 that is suitable for safety-critical work.

The compiler supports a subset of Ada 95 that is defined by the restrictions in Annex H of the Ada 95 Language Reference Manual. This subset is similar to the SPARK subset used to write the HOLD III source code.

To reduce the effort required for certification, almost all of the run-time system was eliminated. The only code that is always required is the start-up code that initializes the stack and calls any library package elaboration subprograms.

Lucas have integrated the compiler with their strict configuration control system, and have demonstrated the generation of application code and supporting documentation to the highest level of the RTCA/DO-178B standard.

The HOLD III program included representatives from the UK military (DERA Boscombe Down) and commercial aircraft certification (CAA) authorities, who were able to advise on the relevance of information offered in support of certification.

The compiler with complete source code and documentation is available on CD-ROM. Ready-to-run binaries are available for the following platforms:

  • Sun SPARC Solaris 2.6 and above.
  • IBM PC GNU/Linux 2.0 and above.