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Last modified on August 8, 1997

GBT Monitor and Control Computer System Design Review

Agenda

Introduction

This design review is being presented by the GBT M&C group, based at Green Bank. The group consists of:

Along with co-op students:

While we are responsible for the content of this review, we wish to acknowledge the contributions of many.

This meeting is intended to review whether the Monitor/Control and Data Analysis hardware architecture will support the software necessary to support Operators, Engineers, and Observers. There is a vary large amount of information to cover, so we should try to limit the discussion to:

GBT M&C Overview

The M&C software is a distributed system consisting of numerous software modules running on multiple computers (Sun SPARC workstations and mv167 single-board computers) communicating over Local Area Networks (LANs). Drawing D35501K011 shows all of the software modules and their interface and communication needs. The mapping of software modules to computers is shown at the end of this section. The system is designed to minimize real-time software dependencies between subsystems, e.g., the only communication needed for control purposes (Manager/Panel Interface). takes place prior to a scan's onset. When stricter real-time deadlines exist between subsystems (Corrector-Correction, Corrector-Focus Tracking, RSI Ethernet Spec Interfaces), a dedicated communication link is used.

A LAN is also used to provide feedback to users in the form of discrete messages (Error & Warning Message Interface) and streams of monitor data (Sampler/Monitor Interface).

Backends which generate low enough data rates (currently the DCR and holography backends) write their data to remote disks using a LAN. Faster backends write their data directly to disk.

Coordinated Universal Time for software use is distributed independently via a network using IRIG to all single-board computers. Network Time Protocol (RFC 1305) is used to distribute time to workstations.

Telescope internal LANs and the site LAN will be separated by a gateway machine whose physical access will be limited to the operator. All control traffic to GBT software will be controlled by the operator. If, by GBT completion the site LAN is not secure, it will be an administrative decision whether to allow remote access to the GBT Control Room computers.

Observer workstations will be capable of running both analysis and telescope interface programs.

The telescope M&C system is distributed over several physically separated rooms on the telescope. Each of these rooms communicates with the others over the Local Area Network.

The following is a list of computers, their locations, and associated software modules.

* not on software interface diagram

Alidade Servo Room

The Alidade Servo Room contains the M&C computers for controlling the front-ends, the LO1 subsystem, and the antenna itself. The equipment provided for this purpose is:

Actuator Control Room

The actuator control room contains the M&C equipment needed to interface the Active Surface controls to the M&C system. This consists of an Ethernet bridge,and an SCRB. The remainder falls under the Active Surface project, and is not discussed further here, except for the network load calculations.

Receiver Room

The Receiver Room M&C equipment consists of only a network drop and an SCRB. All other M&C equipment is remotely controlled from computers in the Alidade Servo Room Five serial ports on the SCRB are allocated for RS-232 interfaces to the feed rotators. A serial link and reset contact are provided for the RSI SCU single-board. An MCB reset contact is provided to reset all the MCB devices. A fiber-optic IEEE-488 bus extender is used to bring the IEEE-488 bus up to the receiver room for controlling the LO1 synthesizers, frequency counter, and spectrum analyzer. A fiber-optic MCB connection is provided to communicate with the receivers and LO1 equipment. Fiber-optic serial connections are provided for use of the RSI SCU. No M&C Computers are located in the Receiver Room because of EMI/RFI concerns.

Equipment Room

The Equipment Room contains the lion's share of the M&C computer equipment. The backends reside here, as well as the IF equipment and the second weather station computer. This is also where all of the computers for recording the data are found. Here is a description of the M&C equipment in this room:

Control Room

The Control Room M&C equipment is used by operators and observers to specify and control observations. Provisions are also made for data reduction and analysis. The equipment specified for the Control Room is:

Telescope LAN

The telescope networks are designed to supply control information to the various telescope subsystems, and to acquire data from the telescope instruments, as well as from the telescope itself. The major architectural feature of the Telescope Lan is that it uses a switched architecture. In a switched network, each computer can be connected to its own segment, which operates at full wire speed, e.g. an Ethernet segment can carry 10 Mb/s, so the computer can use the whole 10 Mb/s. In a normal Ethernet environment, that 10 Mb/s is shared by all the computers on the network. See the
network load calculations. for details.

Workstations

A short synopsis of the functions of each computer is presented here. For information about the configuration of each computer, follow the link on the computer name. Unless otherwise noted, all workstations are stand-alone, that is, they do not depend on the network for booting.

Data Storage

The GBT data will be stored on disks in several different workstations, and will be backed up by an automated tape handling system. 9 GB disks are provided on the Observer's Workstations, and the Data Collection Workstation. A 200 MB disk is provided on the Servo Monitor computer. Several types of data are expected and accounted for:

Embedded Computers

The Embedded Computers perform the task of interfacing to the hardware on the telescope and handling real-time tasks. These computers are all assembled from a common set of VME boards, and run
vxWorks.
Telescope Misc VME Chassis
This chassis is located in the Alidade Servo Room, and controls the front-ends, LO1 system, Receiver Room I.F., and some miscellaneous devices on the telescope. 2 M&C single-boards, and 1 metrology single board reside in this chassis.
Antenna Control VME Chassis
This chassis contains the antenna control SBC, the servo Monitor SBC, and the Laser SBC. These SBC's interact with the antenna servo systems.
Equipment Room VME Chassis
The equipment room VME chassis controls the equipment in the equipment room. There are 2 CPU boards allocated to this function:

SBC Control and Reset Box

This device provides a connection to the single-board computer's reset line, and to the console port. This enables the user to monitor the SBC during reset, before the computer is responding to network logins. The reset line is controlled through an application running on a workstation. Five of these devices have been built, and are under operation in the mockup. The
SCRB Technical Report describes the device more fully. One of these devices can control and monitor up to 15 computers.

Summary

The GBT M&C computer system is designed to be flexible, upgradeable, and reliable. This is assured by the use of: The computers, LAN switches, and data storage devices proposed for the telescope are of the latest design, yet are generic enough that others can be substituted in their place. The network is scalable up to the gigabit level. The computers may be replaced with multi-processor versions, and the disks may be expanded.