A subunit of the CAMAC accelerator control system of ATLAS for monitoring and, eventually, controlling the cryogenic refrigeration and distribution facility is under development. This development is the first application of a philosophy of distributed intelligence which will be applied throughout the ATLAS control system. The control concept is that of an intelligent subunit of the existing ATLAS CAMAC control highway. A single board computer resides in an auxiliary crate controller which allows access to all devices within the crate. The local SBC can communicate to the host over the CAMAC highway via a protocol involving the use of memory in the SBC which can be accessed from the host in a DMA mode. This provides a mechanism for global communications, such as for alarm conditions, as well as allowing the cryogenic system to respond to the demands of the accelerator system

Kawarasaki, Y.

Pardo, R.

Wasniewski, K.

UNT Digital Library

CC&F-850504—45DE85 012372RECEIVED BY OSTi J U N O 3 1985A CAMAC-BASED INTELLIGENT SUBSYSTEM FOR ATLASEXAMPLE APPLICATION: CRYOGENIC MONITORING AND CONTROLR. Pardo, Argonne Nat ional Laboratory, Argonne, IL 60439 USA,Y. Kawarasaki, JAERI, Ibaraki , Japan, andK. Uasnlewski , Argonne National Laboratory, Argonne, IL 60439 USAAbstractA subunit of the CAMAC accelerator control systemof ATLAS for monitoring and, eventually, controllingthe cryogenic refrigeration and distribution facilityIs under development. This development is the firstapplication of a philosophy of distributed intelligencewhich will be applied throughout the ATLAS controlsystem. The control concept is that of an intelligentsubunit of the existing ATLAS CAMAC control highway. Asingle board computer resides in an auxiliary cratecontroller which allows access to all devices withinthe crate. The local SBC can communicate to the host,over the CAMAC highway via a protocol involving the useof memory in the SBC which can be accessed from thehost in a DMA mode. This provides a mechanism forglobal communications, such as for alarm conditions, aswell as allowing the cryogenic system to respond to thedemands of the accelerator system.IntroductionATLAS [1], the Argonne Tandem-Linac AcceleratorSystem, is a major expansion of an existing heavy-ionaccelerator facility which consists of an electrostaticVan de Graaff tandem accelerator and a prototype super-conducting linear booster accelerator. The supercon-ducting linac control system is a CAMAC-based systemwith an enhanced Digital Equipment PDP 11/34 computeras the central control computer. The CAMAC system isconfigured cs a byte-serial multi-crate highway inter-faced to the central computer via a serial highwaydriver residing in a unibus memory-mapped crate.The ATLAS project places a significantly Increasedload on the accelerator control system. This effectoccurs both due to the increased number of deviceswhich must be monitored and controlled but also becausethe much more complex accelerator system requires morecomputing support in order to allow the staff, whichhas not increased in size significantly, to efficientlyoperate the f;:ility.The ATLAS facility contains a number of complexsubsystems which can significantly benefit fromincreased automation and computer control. Subsystemssuch as ion sources, cryogenic distribution system, asuperconducting dipole switching magnet, and sub-sections of the superconducting linac are examples ofcomplex subsystems which require or can dramaticallybenefit from close supervision and control through acomputer system. We report in this paper the firstapplication of a philosophy of expansion using singlehoard couputers ia .specific CAriAC craces to acnievedistributed intelligence in the ATLAS control system.System Design ConsiderationsThere sre many possible approaches which may beused to achieve such a goal and the proper choice isoften strongly influenced not onlyl by local personalbiases but the environment, both hardware and software,which presently exists.The following points were requirements which theenhanced system has been designed to satisfy:I. We felt that the major investment in hardwareand software which had already gone into making ourfacility one of the moat automated heavy-ion facilitiesexisting could not be abandoned. Therefore, theconstraint of building on the ' . ing system was arequirement.2. The load on the central computer due to simplemonitoring tasks should be minimized in order to freethat computer for more complex tasks such as programdevelopment, high level calculations, data management,and human Interfacing.3. The congestion on the serial highway should bekept as low as possible to allow for future activities.It. The reliability of the monitoring and controlof the subsystems mentioned before should be high.This requirement essentially rules out the use of thecentral computer since its reliability Is compromisedby the higher failure rate of disc drives, lineprinters, terminals and other peripherals, not tomention system crashes that occur during suchactivities as program development.5. The operation of the these major subsystemslocally should not be dependent on the operation of theoverall CAMAC highway or the central control computer.The solution which has been adopted at ATLAS is toadd local Intelligence In any CAMAC crate whichcontains ths interfacing hardware for a particularsubsyst*:n. Such a configuration is shown in Figure 1.32CHANNELADCDfiTfl-WAYCOMHLINKCRATECONTBXLEBWITHSBCM/21 :£-•Fig. 1. Hardware configuration for remote intelligenceapplications in ATLAS control system.STRI3UTICM OF TCP, KT-ZZ IS B M UThe local microprocessor is Interfaced Into the desiredCAHAC crate through the use of the auxiliary cratecontroller protocol. Many of the functions of theremote processor require no interface to the centralcomputer. Communication with the central computer isthrough the CAMAC highway using a CAMAC-MA mode intothe micro-processor's memory. This nechanism allowsthe use of LAH's as interrupts for both CPU's as wellas allowing essentially transparent polling of systemstatus for data logging In the control room, directcommunication to the operator fron a remote site(home), and central data base updates. By maintainingall systems as integral parts of the serial highway, itis possible to develop more complex, seldom usedroutines which use various hardware components of thesubsystem in a way that is often transparent to thelocal microprocessor. An example of this last featureIs the measurement of the Q of a resonator using thecryogenic thermometry which is actually part of amicroprocessor subsystem.All choices have disadvantages.of this approach Include:The disadvantages1. The elaborate libraries of control functionswhich have been developed for our RSX-based systemcannot be used in the microprocessor environment wehave chosen. Therefore program development has beenslower than might have been otherwise possible.2. Each subsystem is essentially limited to oneCAMAC crate. This disadvantage can be overcome withthe use of a local branch highway and Is being done inour ion source subsystem, but it is not possible for amicroprocessor to access another crate on the mainaccelerator CAMAC serial highway except through anelaborate communication sche.ne involving the centralcomputer.Hardware and Software ImplementationThe microprocessor chosen for implementing thisconcept was the Digital Equipment SBC 11/21 (Falcon)single board computer. The Falcon is easily con-figurable in a number of memory modes. This allowsdevelopment and debugging using RAH memory which canlatsr be converted into PROM memory allowing completestand-alone operation independent of the rest of thecontrol system. The Fsicon resides in and Is inter-faced into the CAMAC crate through a Kinetics System3921 crate controller operating in the auxiliarymode. The CAMAC-DMA unit is a Kinetics System 3825Da taway Communications Link. This system is installedin a CAHAC crate which is a part of the acceleratorcontrol system serial highway.The software development environment selected isPascal with parallel features similar to Module. Thissoftware runs under the RT-11 operating system and hasfeatures quite similar to DEC's Micropower Pascal. Thesoftware runs in the Falcon with no operating systemand, in the final version, will execute immediatelyupon bootup.During the development period, which we are stillin, the executable code is complied and linked on theprogram development computer system and then downlineloaded into the SBC 11/21 using the features availablein the ODT PROM on the 11/21. The debugging cycle canactually include execution of the code on thedevelopment computer under RT-11 prior to testing inthe target system. This feature is accomplished viaswitches in the compile and link cycles.The Cryogenic Monitoring and Control SystemThe cryogenic monitoring and control system is thefirst application of the design philosophy describedabove. The implementation of this system has allowedus to break the task into three phases which will beFig. 2. Terminal interface for ATLASmonitoring and control subsystem.cryogenic Fig. 3. ATLAS cryogenic monitoring and control CAHACcrate showing auxiliary crate controllerhousing single board computer.described below. Phase I is essentially complete andPhase II is in the early stages of development.The ATLAS cryogenic system [2] consists of twoseparate liquid helium refrigerators (an additional oneIs planned), an elaborate liquid helium distributionsystem with a total length of nearly 200 feet, twolarge helium dewars, and an associated liquid nitrogendistribution system. This system provides thenecessary cooling for ATLAS which consists of 47superconducting resonators, 22 superconducting sole-noids, and a superconducting beam switching dipolemagnet. The total number of parameters which should bemonitored iu the system is raoTe than seventy. Theseparameters are temperatures, pressures, flow rates,liquid levels, compressor operation, and some miscel-laneous information. Presently the system operates inan intensive manual mode. The only automatic featureIs the control of heaters, located in the main dewarreservoirs, based on cither liquid level, pressure, orflow rate. Unfortunately the complexity of the systemcauses this simple regulation to be an inadequatecontrol under varying load conditions of the accel-erator, thereby requiring intensive human interactionfor most situations.This research w.'s supported by the U.Department of Energy under Contract U-31-109-Eng-38.S.References[1] J. Aron, et al. "StatusProject", this conference.of the ATLAS12] J. M. Nixon and L. «. 3ollinger, "Cooling theArgonne National Laboratory SuperconductingHeavy-Ion Llnar. with Two Refrigerators inParallel", Advances in Cryogenic Engineering,27, (1982) 579.The Phase I control system development goals wereto implement a stand-alone monitoring system for theATLAS cryogenic system. The parameters to be inter-faced and the basic software required are now in placeand have been functioning for three months. A localterminal is provided which provides graphical andtextual display of system temperatures, pressures, andliquid levels. The terminal keyboard is used toprovide input of allowed ranges, to activate limitchecks on desired parameters, and control the displayedinformation. The terminal is Interfaced through one ofthe two serial ports available on the Falcon. Theterminal interface is shown in Figure 2 and the CAMACcrate housing the micro-processor is shown in Figure 3.The system is presently running from RAM memory but itwill be converted soon to PROM memory configuration forthe program and RAM for the data regions only.The goal for Phase II is to provide communicationback to the central control computer to allow datalogging, global alarm condition broadcasting, andremote site communication. This phase of developmentwill employ the dataway communication* link, a CAMAC-DMA device which allows IMA access to the memory of thelocal microprocessor in order to communicate and toretrieve data concerning the subsystem parameters. Fordata logging functions, the central computer canextract Information from the microprocessor memorywithout the need for any communication softwareInterface. Similarly, for error condition reportingthe microprocessor can interrupt the central CPU bysetting a LAM in the CAMAC crate and loading the errorinforaation into a predefined region of utaory.Therefore in Phase II communication the problems ofasynchronous communication can be avoided. The needfor such communication will surface later in the PhaseIII period when actual automatic control is attemptedand the need for remote operator Input nay becomedesirable. Phase II implementation should occur duringthe next six Months.The third phase will be to implement certaincontrol features on the cryogenic system. A moreelaborate heater control allowing regulation based on anumber of parameters and some Additional control ofspecific valves and loading of compressors may also beincluded. The details of this effort will requireintensive implementation and testing cycles which awaitthe full implementation of Phases I and II.p>P3

CAMAC-based intelligent subsystem for ATLAS example application: cryogenic monitoring and control

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CAMAC-based intelligent subsystem for ATLAS example application: cryogenic monitoring and control

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