Introduction To EPICS

The "Standard Model" for Control System Architectures in the `90s'
"Standards based"
- Unix/X-windows
- Ethernet/FDDI and TCP/IP
- VME
Client/Server Model
Distributed Real-time Process Variable Database (No central database)
Scalable from [1 workstation/1 ioc] to [15 workstations/8 X-terms/110 IOCs] (at least)

Architecture and Tools

EPICS - Supported Hardware

Workstations(2)
- Sun (SunOs, Solaris)
- HP (HPUX)
- Silicon Graphics (Unix)
- DEC (VMS and OSF1)
- PC (Windows NT, 3.1, `95, Linux)
Input/Output Controllers
- VME/VXI based CPU's (680X0 CPU's...) running vxWorks
- Discussions about the PowerPC, Pentium, MIPS
IO Types (here at ANL)
- VME I/O
- VXI I/O (MXI bus connection/mapping)
- GPIB Instruments
- Bitbus
- RS232/RS422 Instruments
- Allen Bradley Data Highway (1771 series I/O)
- CAMAC
Fieldbus Survey

EPICS - Software Tools (Channel Access)

The Software Bus

Clients (requestors) and Servers (providers)
Based on the Process Variable (PV) Name (28 character string)
Operations include Search, Get, Put, Add Event (add monitor)
"Monitors" send data to the client only when it has changed
Attributes include Alarm Status, Units, Precision, Time, Enumeration Strings, Graphic Limits, Control Limits, Alarm Limits
Full Channel Access Library and an EZCA Library

Architecture and Tools

EPICS - Software Tools (IOC)

Definitions
- IOC: Input/Output Controller
- Record Type: A previously defined `building block' with a unique structure of fields and a unique processing routine to accomplish a specific function. `Record support' refers to the processing routine and the definition of the structure (e.g. an analog input record is used to monitor an analog signal, convert it to engineering units, check the value against alarm limits, and notify interested channel access clients of any significant change)
- Record: A particular instance of a `Record Type' with appropriate values entered into appropriate fields
- Database: A collection of `records'
- Scanned (processed): Executing the record processing routine (unique to a record type) for a particular record
The IOC's fundamental responsibility is to input data from the `process' (and/or the operator), manipulate it in a predefined manner, and <optionally> output data to control the `process'
Inputs, data manipulation, and outputs are defined by the `Application Developer' by configuring `records' that become part of the IOC's database
The IOC's primary task is to `scan' the database, deciding when to and knowing how to execute predefined records
Records can be linked together to create control algorithms and sequences
Input and output records have a field in which to specify the `device type'.

IOC Internals

Database Record Types by Category

INPUTS	ALGORITHMS	OUTPUTS
Analog Input	Calculation	Analog Output
Binary Input	PID	Binary Output
Muli-bit Binary Input	Signal Select	Multi-bit Binary Output
Digitized Analog Input	Data Compression	Stepper Motor
State	Subroutine	Timing Signal
String Input	Fanout	Permissive
Long Input	Histogram	String Output
Pulse Counter		Long Output
		Pulse Train
		Pulse Delay

Analog Input Record

struct aiRecord  {
  /* start of ai specific fields */ 
  double  val;  /* Current EGU Value */
  struct link  inp;  /* Input Specification */
  short  prec;  /* Display Precision */
  unsigned short  linr;  /* Linearization */
  float  eguf;  /* Engineer Units Full */
  float  egul;  /* Engineer Units Low */
  char  egu[16];  /* Engineering Units */
  float  hopr;  /* High Operating Range */
  float  lopr;  /* Low Operating Range */
  float  aoff;  /* Adjustment Offset */
  float  aslo;  /* Adjustment Slope */
  float  smoo;  /* Smoothing */
  float  hihi;  /* Hihi Alarm Limit */
  float  lolo;  /* Lolo Alarm Limit */
  float  high;  /* High Alarm Limit */
  float  low;  /* Low Alarm Limit */
  unsigned short  hhsv;  /* Hihi Severity */
  unsigned short  llsv;  /* Lolo Severity */
  unsigned short  hsv;  /* High Severity */
  unsigned short  lsv;  /* Low Severity */
  double  hyst;  /* Alarm Deadband */
  double  adel;  /* Archive Deadband */
  double  mdel;  /* Monitor Deadband */
  double  lalm;  /* Last Value Alarmed */
  double  alst;  /* Last Value Archived */
  double  mlst;  /* Last Val Monitored */
  double  eslo;  /* Rawto EGU Slope */
  long  roff;  /* Raw Offset */
  caddr_t  pbrk;  /* Ptrto brkTable */
  short  init;  /* Initialized? */
  short  lbrk;  /* LastBreak Point */
  long  rval;  /* Current Raw Value */
  long  oraw;  /* Previous Raw Value */
};

EPICS - Software Tools (Application Developer)

Database Configuration (DCT, GDCT, CAPFAST)
State Notation (State Machine) Language
Graphical Display Editors (MEDM, EDD)
Channel Access Library and EZCA

EPICS - Software Tools (Extensions)

Usually Channel Access Clients that need data from the IOCs or have data for the IOCs

Graphical Display Tools
Alarm Manager
Archiving tools
Backup/Restore
Macros/Scripts
Commercial Applications with interface routines
...

An EPICS Application

EPICS - A Collaboration

Initial collaboration between Los Alamos National Lab (Ground Test Accelerator) and Argonne National Lab (Advanced Photon Source)
Other major DOE sites
- Lawrence Berkeley
- Stanford Linear Accelerator Collider Lab
- CEBAF
- Brookhaven National Lab
Other DOE sites/Non-DOE sites/International sites
- See attached list
Quarterly "collaboration" meetings at different sites (see example agenda)
- Application Discussions
- System Development/Evolution Discussions
- Training/Tutorials
EPICS List Servers (send e-mail to "listserv@aps.anl.gov" for more info)
- tech-talk (internals)
- epics_applications
- beamline_controls
- archives at Lists

Collaborators (as of 5/1/96)

Colliders	Detectors	Commercial
The_Advanced_Photon_Source (ANL)	Halls_A,_B,_and_C_Slow_Controls (CEBAF)	The High Power Laser Experiment (Boeing)
The Advanced Light Source (LBNL)	Advanced Light Source Beamlines (partial) (LBNL)	Wafer Fabrication Plant (AMD)
The Tesla Test Facility (DESY)	Gammasphere (LBNL)	Liquefied Nature Gas Plant (Baltimore G&E)
The Continuous Electron Beam Accelerator Facility	Advanced Photon Source Beamlines (ANL)	Tunnel Fire Ventilation Test Program (DOT/Bechtel-Parsons-Brinkerhoff)
The Bates Linear Accelerator (MIT)	The PHENIX detector system for RHIC Slow Controls (BNL/LANL)	Flexible Manufacturing Facility (Allied Signal)
RF for Next Linear Collider (SLAC)	The STAR detector system for RHIC Slow Controls (Creighton/U. Wash/Kent State/UCLA/LBNL)	Wastewater Treatment (Western Lake Superior Sanitary District)
DAHRT (LANL)	The Biotechnology Beamline (SSRL)	Potable Water Distribution (St. Louis County)
The Advanced Free Electron Laser (LANL)	The BaBar detector for B-factory Slow Controls (SLAC/LBNL)	Compressor Control (Baltimore G&E)
The HERA cryogenic plant (DESY)	Structural Biology Research Group (Riken)	GM Fuel Cell Program (LANL)
The Intense Pulsed Neutron Source (ANL)	NASA Langley (wind tunnels)	Plant Simulation (Knolls)
Free Electron Laser (Budker INP		Flight Simulation (JPL)
The Tesla Test Facility Injector (SACLAY)	Telescopes	Fuel Depots (US Navy)
Racetrack Microtron (U/Ala)	The Gemini 8-M Telescope (AURA)	Product Storage/Movement Facility (Citgo)
The Free Electron Laser Program (Duke)	Kitt Peak Observatory (NOAO)	Ground Tracking Station (NASA Canberra)
The Heavy Ion Fusion Test Stand (LBNL)	The United Kingdom Infrared Telescope upgrade (JAC)	Well Head/Extraction (Saphania Oil Field)
RF and feedback for B-factory (SLAC)	The William Herschel Telescope/WFFOS instrument (INGT)
The Average Power Laser Experiment (LANL)	The Keck II Telescope (CARA)
LAMPF/LANSCE (LANL)	LIGO (CalTech)
Advanced Light Source (partial) (LBNL)
National Laboratory for High Energy
Physics (KEK)
Berlin Electron Synchrotron Light Source (BESSY II)
Microtron Project (IASA)
RF (PSI)

Suppose I wanted to ...

... monitor and interact with my equipment
- Define records/devices for each point to monitor and control
- Create a Display Manager screen that connects to the PV's
- Use any other EPICS compatible tool to access the PV's
... create a closed loop algorithm to maintain the temperature of my soup at 155 degrees.
- Define a record to monitor the temperature and to control the temperature.
- Define a PID record in the IOC or write a program on your workstation to implement your desired algorithm or add channel access capabilities to a third party `closed loop control' package.
... inhibit control of certain process variables from certain users
- configure the channel access security feature of EPICS
... record the settings of 1500 Process Variables so I can return to this setup tomorrow.
- use BURT
... acquire and store 100 MBytes of data in 10 seconds or less
- design a data acquisition system
... add my own support for records or devices
- follow the rules and you get alot `for free'
... get more information about obtaining EPICS.
- Mail to:Bob Dalesio - LANL

Footnotes

(1): Reference: Overview of the Experimental Physics and Industrial Control system: EPICS by Steve Lewis, LBL
(2): Sun and HPUX have the most complete support, others are partial support of certain tools

Introduction To EPICS

Table of Contents

Footnotes