2 OVERVIEW

The base for development of VLT applications is CCS on the workstation and LCC on the LCU.

CCS and LCC is a set of relatively independent modules providing a standardized access to different resources.

CCS and LCC are intermediate layers of software, composed of libraries for the programmatic side, configuration utilities for the interactive part, and servers and daemons for the background support, isolating the applications and high level control software from the operating system.

The following modules are included:

On Line Database

The On-line database provides the mechanisms to organise, store and share data.

Message System

Provides a homogeneous interprocess communication mechanism, on a single computing unit as well as across the network.

Scan System

The Scan mechanism provides a bidirectional way to exchange data between workstations and to copy data from the LCUs to the workstations.

Time System

Provides the Universal Time (UTC) allowing synchronization of processes within one processor and between processors.

Booking System

Allows dynamic (re)allocation of VLT resources for exclusive or shared use and checking of access permissions.

Logging System

Provides facilities to keep trace of important events occurring in the system.

Error and Alarm System

Allows logging of errors, their display and the management of alarms.

Portable User Interface Toolkit

Provides the basic tools to build a homogeneous man-machine interface on the workstation.

Engineering User Interface

Allows the user to send command/receive replies from any process on any node.

The LCU also provides the following modules, not present on the workstation

LCU Manangement

Provides management of the LCU node, i.e. start-up and shut-down sequences.

I/O signal handling

Provides symbolic, transparent access to signals.

Command Interpreter

Provides a table driven command parser.

Motor Control

Provides a versatile and hardware independent access to motors.

Drivers

LCC also includes drivers for ESO standardized VME boards.

The message system and the on-line database are the only mechanisms used by applications to exchange information.

Figure 1 shows the relation between CCS, LCC and applications on the workstation and on the LCU.

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Figure 1: CCS - LCC overview

CCS and LCC are also connected through specific interfaces shown in figure 2.

Commands are sent from the workstation to the LCU through the message system. The LCU sends back one or more replies to each command received.

Logs and error logs from the LCU are sent as messages to the CCS log manager, which stores them on disk.

The scan system scans data from the LCU database to the workstation database.

Figure 2: Data flow between LCC and CCS

Many interfaces and internal structures of CCS and LCC are compatible or identical. The modules with identical interfaces are:

· on-line database

· message system

· time system

· booking system

· logging system

· error and alarm system.

A more detailed overview of the common software can be found in [1], [2] and [18].

2.1 Getting Started

Before you continue reading this manual, please read the VLT Common Software Overview [18]. This manual gives an overview of the VLT software and in particular chapter 3 describes how to organize and start the development process. It also describes templates available for different parts of the development process.

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