Excelsior Eases Migration of Aerodata's Core Software To a New Platform
Using a custom version of Excelsior's Native XDS-PPC Modula-2 compiler, Aerodata
Flugmesstechnik was able to rapidly migrate its MODAMS core to the new hardware
platform with minimal changes. "We needed it to run on the more powerful PowerPC
CPU, but our legacy Modula-2 compiler did not support that processor and was no
longer maintained by the vendor," said Ludger Mastall, Manager Software Development
for Aerodata Flugmesstechnik. "Without Excelsior's help, we would have to rewrite
everything in C by hand, which would greatly increase costs and possibly compromise
delivery times in the big contract we were recently awarded by the Japanese Aviation
The system engineering company Aerodata Flugmesstechnik GmbH, founded 1985,
is the kernel of the Aerodata Group - the world leader in manufacturing airborne
equipment for the safety inspection of air navigation infrastructure and the largest
corporate supplier of associated flight inspection services. As a technology
oriented aviation system company and GPS applications pioneer, the group supplies
products and services for air traffic control as well as a wide variety of airborne
special mission solutions.
The core of Aerodata's Flight Inspection System is the software package known
as MODAMS (Modular Online Data Acquisition Monitoring System). MODAMS performs
parallel computer processes in real time: operator dialogue, monitoring processes,
data processing and data storage. The system displays electronic maps in the
aircraft cockpit or at the operator's console which enhances information exchange
between the flight crew, pilots, and flight inspectors. This, in turn, further
enhances the efficient operation of the system.
MODAMS was originally designed to run under DEC RT-11 on PDP-11 based systems
and then ported to Microware's OS-9 for Motorola 680x0 series CPU. For the new
generation of Flight Inspection Systems, in which real time data acquisition
and navigation calculation will be done on the same computer, Aerodata had
selected the more powerful PowerPC 8240 CPU. The problem was that the MCS
Modula-2 compiler, which Aerodata had been using for MODAMS development, did
not support PowerPC. "We had about half a million lines of Modula-2 code and
almost no means to get them running on the new platform," said Mastall, "except
by manually rewriting everything in C or C++".
Excelsior had made an offer to Aerodata to create a custom Modula-2 compiler
for their new target. Excelsior's proprietary XDS compiler construction framework,
among other components, contains a Modula-2 front-end and PowerPC code generator.
It allowed Excelsior to quickly create a reasonably priced optimizing Windows
NT-hosted Modula-2 cross-compiler targeting OS-9 for PowerPC. It was named Native
XDS-PPC after its counterpart Native XDS-x86, available on the market since 1996.
Excelsior XDS Modula-2 compilers comply to the ISO 10514 International Standard,
whereas MCS belongs to the pre-ISO generation and also has its specific language
extensions and library modules. This could potentially lead to an enormous amount
of source code changes during migration thus greatly reducing the reliability of
MODAMS. To help Aerodata solve this problem, Excelsior had customized the compiler
and the run-time library, making them more compatible with MCS. As a result, most
of Aerodata's source code could be passed through the XDS compiler without changes,
and only a few low-level CPU-dependent modules needed complete rewriting. "We have
managed to find the right balance between the amount of the XDS system
customizations and the amount of required changes in our source code, thus
minimizing costs and delivery time", said Mastall.
After the approach proposed by Excelsior has proved its viability, Aerodata
immediately purchased two additional licenses for the Native XDS-PPC compiler.
"Now we know whom to contact first, have our programmers a need for a custom
development tool," said Dr. Manfred Haverland, Managing Director for Aerodata