HONEYWELL
Aerospace Electronic Systems
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future to define Warm and Hot spare requirements. This effort has not yet started. As the Mark III CMU
hardware was designed to support Dual capability, Updated dual capability could be provided with a software
upgrade.
Ethernet
ARINC 646 defines an Ethernet Local Area Network (ELAN) aboard an aircraft. The Mark III CMU provides
four 10BaseT Ethernet ports that can be used for various applications which could include Gatelink
connectivity, ARINC 615A data loading, ARINC 744A printer and ELAN connectivity. Software support for the
Ethernet ports will require a software upgrade.
MIL-STD-1553B
Mil-Std-1553B is a military standard interface used to communicate with onboard end systems such as an
FMC, MCDUs and remote annunciators. This hardware interface is only available in the military version of
the Mark III CMU. Software support of this interface requires a software upgrade. This is applicable for only
specific Military aircraft.
Debug Maintenance Terminal (DMT) / Data Logging Terminal (DLT)
A Debug Maintenance Terminal and Debug Logging Terminal can be used to access BITE information,
program the APM, and for general debug capability. The Mark III CMU provides two RS-232 ports that can
be used for a DMT and a DLT. The RS-232 ports are accessible both from the front and rear connectors and
can interface with a laptop computer executing terminal emulation software. The DMT is a device that is
used for Honeywell debugging and testing, and is not a device required by our airline customers.
Data Loader
The Mark III CMU supports an interface to both an ARINC 615 compliant Airborne Data Loader (ADL) and an
ARINC 615 compliant Portable Data Loader (PDL) via high speed ARINC 429. The ADL interface is
accessible through the rear connector while the PDL is accessible from the front connector.
High speed data loading via PCMCIA and Ethernet are software growth options.
PCMCIA
The Mark III CMU hardware is equipped with a PCMCIA interface that can be used, to provide a faster
means of data loading than an ARINC 615 data loader. The PCMCIA interface is accessible only from the
front panel. PCMCIA is Honeywell’s recommended method of performing complete full software loads.
OOOI
The Mark III CMU provides up to 6 high speed ARINC 429 inputs and a number of analog discrete inputs that
can be used to determine Out/Off/On/In events. Data available on these interfaces typically include oil
pressure, weight on wheels (WOW), flaps, parking brake, and doors.
2.3 Software Overview
In order to meet the system/safety requirements of future CNS/ATM upgrades, all of the Mark III CMU
software has been developed to support a future DO-178B Level C. Today, the Mark III CMU is certified to
Level D, which is the standard used for certification of ACARS and CMU units. Partitioning in the Mark III
CMU is supported by the DEOS operating system which has been previously certified to DO-178B Level A.
The underlying fundamental goal for the Mark III CMU software development was to develop a single software
system that could be used with minor modification on other platforms. Honeywell was able to achieve this
goal through the use of advanced software development techniques, including model-based development.
The model-based approach allowed the developers to design the system independent of the target hardware,
capturing the requirements in a model database. The requirements/design are then turned into source code
