I.B. + M.A. DE LANDE LONG
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Telecommand Decoder Shell package - Detailed description

The Telecommand Decoder Shell is a software package, designed to be built into a software system for a telecommand application. The part of the software system which lies outside the Shell is called the Telecommand Decoder Environment. The API (Application Programming Interface) consists of function calls between the Environment and the Telecommand Decoder Shell.

Telecommand interfaces in the API

(shown by left-to-right arrows in the diagram)

The Environment calls the Shell to:

pass CLTUs to the Shell
pass candidate BCH codeblocks to the Shell
fetch Communications Link Control Words (CLCWs) from the Shell.

The Shell calls the Environment to deliver packets and other data units to the Environment.

Telecommand Decoder Shell software i/f

Management interfaces in the API

(shown by downwards arrows in the diagram)

The Environment calls the Telecommand Decoder Shell to:

initialise, configure and terminate the Shell
pass control of the CPU to the Shell (scheduling)
get optional status reports

The Telecommand Decoder Shell calls the Environment for storage allocation and for the optional logging of messages.

Other interfaces in the API

In addition to the function calls shown in the diagram, the Shell has interfaces for the optional features:

Failure simulation for test systems (BIFs: Built-In-Failures)
Telecommand Authentication with ESA AU
Segment Level Security Interface (SLSI) for external implementation of security features

Telecommand Decoder Shell Package

The Telecommand Decoder Shell package consists of:

a set of C header files defining the interfaces
a sample user program to demonstrate use of the Shell, including examples of all the Environment functions which are called by the Shell
a library of modules implementing the Telecommand Decoder Shell
the Telecommand Decoder Shell Software User Manual.

A telecommand system built with this package is likely to be very much cheaper than independent development of an equivalent capability.

Licensing and support may be negotiated according to requirements. All the telecommand features are included in the standard Telecommand Decoder Shell licence. The ESA Telecommand Authentication and the SLSI security interface are licensed as optional extras. The Built-In-Failures capability is available on request.

The Telecommand Decoder Shell consists of approximately 8,000 lines of C code divided into about 120 modules. All code is written in ANSI/ISO 9899-1990 C and is highly modular and easy to maintain. The code makes no use of any library calls. It is therefore easily portable to different computer architectures.

It has been demonstrated running on processors from HP, Intel, Motorola, Silicon Graphics, Sun and many others.

The code has been compiled by at least six independent ANSI C compilers and the demonstration program produces identical results in each case.

Please contact us for further information on technical questions or licensing conditions for the Telecommand Decoder Shell package.

TC Decoder Shell TC Encoder Shell TC Features TC Architecture