CMU software – overview
Each CMU system is made up of two software elements (diskettes), the Operational Software Diskette and the Customer Unique Database Diskette. Both must be downloaded into the CMU prior to operation.  Once the two diskettes are loaded, there is no need to reload the CMU unless it is installed on a different aircraft type (such as from a 747 to a 737 aircraft). However, the two diskettes are the databases and therefore may be updated periodically to support the changing needs of the airlines.  Conveniently, the Operational Software changes less frequently and may be valid for several years.
The CMU software can be downloaded using the Airborne Data Loader installed in the aircraft or the Portable Data Loader. The difference between the two is that a Portable Data Loader is connected to the CMU’s front panel connector using a PDL-to-CMU adapter cable (part number 704-2619-002) during the downloading process.
Once the software has been downloaded into the unit, the software will remain unaltered in the unit even if the CMU is removed from the aircraft.  When the unit is removed from the aircraft, only the existing uplink and downlink messages currently in the CMU’s memory are automatically deleted.
Software Installation

Operational Software
Operational

Boot Software (from Operational Software Database
Factory) (Core + App)
Portable Data Loader
Adapter Cable P/N 704-2619-502
Software Installation
A detailed description of the procedure used for loading software and databases into the Mark II CMU is contained in the Component Maintenance manual or in the Software Installation documents. It is recommended that the individuals loading the software be familiar with the steps outlined in the two documents.  Initially the Mark II CMU must be loaded, by the user, with Core/Application software and database, (these are supplied as individual diskettes with the unit).  Subsequent changes to the database are the modifications required by the individual user.  Loading of the software may be accomplished via the connector on the front of the CMU by the use of a Portable Data Loader (PDL) or alternatively via an Airborne Data Loader (ADL).
It is also possible to load the Mark II CMU using a PCMCIA.  As the PCMCIA is significantly more expensive than the 3.5 diskette, this method of installing the Mark II CMU is not included in this document.
Note: a CMU adapter cable (AlliedSignal PN 702-2619-002) is required if a PDL is to be used to load the unit.  Prior to installation, if a PDL will be used to load a unit, verify that you have ordered and received such a cable, as these are sold separately from the unit.
Note: that in the event of a fault in the upload process, indicated by the Data Loader XFER fail indicator on the Data Loader panel, the CMU front panel display also provides error LEDs.
CMU Software Downloading via fixed Airborne Data Loader
　
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