Telecommand Encoder Shell package - Detailed description

3. Telecommand Encoder Shell Package
 

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

1. Introduction

The shell is a software component which contains the complexity of the telecommand protocols, including the TC Space Data Link Protocol and the COP-1 (Communications Operation Procedure). It is easy to integrate into a system and is ideal for building:

• spacecraft control systems
• spacecraft ground testing systems (EGSE)
• simulators
• training systems for spacecraft operators.

The Telecommand Encoder Shell accepts service requests for the telecommand services and returns responses to the requests:

• MAP Packet (MAPP)
• MAP Access (MAPA)
• Virtual Channel Packet (VCP)
• Virtual Channel Access (VCA)
• Virtual Channel Frame (VCF)
• Master Channel Frame (MCF)
• COP Management (COPM), used for passing directives to COP-1

(See the separate description for details of this and other Packet Telecommand features supported by the Telecommand Encoder Shell.)

The Shell delivers Communications Link Transmission Units (CLTUs), ready for serialisation and transmission. The Shell also accepts Communications Link Control Words (CLCWs) from the spacecraft telemetry.

Telecommand Interfaces to Telecommand Encoder Shell

2. Telecommand Encoder Shell Software Interfaces

The Environment calls the Shell to:

• make service requests to the Shell
• deliver Communications Link Control Words (CLCWs) to the Shell
• handle flow control for Communications Link Transmission Units (CLTUs).

The Shell calls the Environment to:

• provide responses to service requests
• pass indications to the Environment (Alert, Suspend)
• deliver CLTUs to the Environment.

There are management interfaces in the API. The Environment calls the Shell to:

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

The management interfaces from the Shell to the Environment include calls to the Environment for storage allocation and for the optional logging of messages.

The Shell also provides support for ESA Telecommand Authentication as an optional extra. When this option is selected, there are additional functions in the API.
 

3. Telecommand Encoder Shell Package

• 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 Encoder Shell
• the Telecommand Encoder 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 Packet Telecommand features are included in the Telecommand Encoder Shell; the only exception is ESA Telecommand Authentication, which is licensed as an optional extra.

The Telecommand Encoder Shell consists of approximately 10,000 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 calls to the operating system run-time libraries. It is therefore easily portable to different computer architectures.

It has been demonstrated running on processors from Hewlett Packard, Intel, Motorola, Silicon Graphics and Sun.

The code has been compiled by at least nine 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 Encoder Shell package.

TC Encoder Shell     TC Decoder Shell     TC Features     TC Architecture