IEEE Transactions on Nuclear Science, Vol. NS-34, No. 4, August 1987

TFTR CAMAC SYSTEMS AND COMPONENTS

William A. Rauch, William Bergin, and Paul Sichta

Princeton Plasma Physics LaboratoryPrinceton University

Introduction

Princeton's tokamak fusion test reactor (TFTR)utilizes Computer Automated Measurement and Control(CAMAC) 1 to provide instrulmentation for real an(d quasireal time control, monitoring, and data acquisitionsystems. This paper describes and (liscusses thecomplement of CAMAC hardware systems and componentsthat comprise thle interface for tokamak control andmeasurement instrumentation, and communication withthe central instrumentation control and dataacquisition (CICADA)2 system. It also discusses CAMACreliability and calibration, types of modules used, asummary of data acquisition and control points, andvarious diagnostic maintenance tools uised to supportand troubleshoot typical CAMAC systems on TFTR.

87x0294

_=] ~~~VAX CLUSTER|

CCI CCICCI CLI CII 1.1.1 III~~~~~~~~I

LINK|HES || TSS

SAI LINKS uVAX uVAX BVAXLINK

MEMORY |kmXp X1 0

CAAL CAMACCAAC CAMACCAMAC CAMAM uVAX CCMAC LINKS

CONSOLE LINK |sbPS c a 4 C l

SAFETY th BOcK Trnf(KSBTU2 lk N

thecc cCI CADA centra stemcomuesFig. 1 TFTR CAMAC:link configuration, 8CAA

AsubsysCteCmACAAIoptrsICAMA CAA CMCAZ& ik r

connec ted to the Micro-VAX computers . AKparallel data acquisition link is providled bythe Block Trat:sfer (BTU) link connected tothe CICADA central sys tem coinpllters .

TFTR CAMAC Link Con-figuratLion

Equipment Corporation (DEC) Micro-Vax computers via KS2060 CCI ' s. In addition the CAMAC connected to theGould/Sel computers is linked via a separateblock transfer link which is returned through the HostInterface Module (HIM) directly to the Gould/Selcentral system computers.

TFTR CAMAC Link Architecture

A description of the TFTR CAMAC link architectureprovides a basic understanding of CAMAC systemconfigurations and implementation. The CAMAC link canhe characterized as a two signal system comprised of a

bit serial hi-phase data signal and 5MHz data clocksignal. The real CAMAC link throughput rate isapproximately 12 Kbytes per second (compared withBlock Transfer rate of 250 Khytes per second shown onFig. 5). A third signal, the facility clock, isencoded with operational events and is the tokamakreference for timing and digitizing rates. This is a1 MHz bi-phase encoded clock link that is distribu-tedto all crates that require a clock provision.

#87Xo296

The diagram of Fig. 1 depicts an overall view of tneTFTR CAMAC3 configuration. It shows several CAMAC bitserial highways (CA.MAC links) connected to Gould/SelConcept 32/77 computers via the CAMAC ComputerInterfaces (CCI). A Kinetics system (KS) 2070 serial

hnighway driver provides the CCI interface betweengould/Sel subsystem computers and the CAMAC link. Theinterface provides: (1) pipe lining of CAKAC transfer;(2) returning a quality bit for each executeld CNAF to

ensure data integrity; (3) support for demand messaqesand; (4) retuLrnling Q response for each executed CNAF.

Also shown are four 'highways which may he operatedeither bit-serial or byte-serial, connected1 to Digital

Fig. 2 Typical CAMAC linik configuration. A miaximumnumber of 62 crates per link are connected to

the Gould/SET computers. Real throughpultrate is 12 Kbytes per secondl.

The diagram of Fig. 2 depicts a typical rFTR Gould/SelCA.MAC link. The maximum nuimber of crates per link. is

62. A sumlnSary of the total number of crates on lineat TFTR is given in Table 1 . As shown the TFTR

0018-9499/87/0800-0970$01.00 © 1987 IEEE

970

971

specifiepd 313 U-port module, M352 optic module, and3952 Kinetic Systems crate controller are usedthroughout the link to interface the on-line crates.The optic module transmits and receives the link whereisolation, grounding, or link distance dictates itsapplication, and also has battery backup.

Furthermore the U-port is a multiple function modullewlhich reformats the data into bi-phase and NRZ (non-retuirn zero) format dependent on where in the link thedata is being transmitted or received. The bi-phaseformat is necessary because of the transformercoupling of the U-port and optic module I/O. Itreceives and re-transmits the CAMAC data, CAMAC dataclock, facility clock, and provides automatic cratebypass capability in case of loss of power in order toprevent loop collapse. In addition the U-port putsthe facility clock signal onto the CAMAC crate P1 busline, and also decodes the facility clock signal intoa 1MHz clock reference which it puts on the P2 line.Also, in the event that the facility clock signalshould be interrupted, the U-port automatically putsan internally qenerated 1MHz crystal clock on both theCAMAC P1 and P2 lines to allow all timing modules totime out and complete their respective cycles.

#87X0297

host computer system also includes the block transfersystem. The block transfer .system consists of asynchronous data link and a common host interfacemodule connected to four central level Gould/Selcomputers, see Figs. 1 and 4. The block transfer linkparallels portions of the CAMAC link andi provides analt,ernate path for transferring the large blocks ofdata collected in local CAMAC memories locatedthroughout the diagnostic systems of TFTR. Thissystem enhances the subsystem CAMAC facilities toaccomplish data acquisition and storage qoals of 20Mbytes of data per shot. The HIM can support up toeight Gould/Sel computers. The block transfer unit(BTU), shown in the (diagram of Fig. 4, acts as anauxiliary crate controller, and has the capability tosupport up to 225 units. The present TFTRcommunication link is supporting 69 BTU's. Thecommunication is via a hit serial bi-phase data linkand asynchronous 2.5 MHz data clock. The transmissionmedium is optical and electrically (isolated), thesame technique as with the CAMAC links. Because otburst mode data transmission and efficient serial linkprotocol, throughput yields approaching 250 Kbytes persecond can be obtained, see the curve shown on Fiq. 5.

#86EOola

COMPUTER ROOM

BTU- Block TransferUnit

L2CC- Crate ControllerType L-2

FromFacility Clock

Pig. 3 Micro-VIAX CAMAC link confiquration. ThisThomson Scattering link is typical for allTFTR Micro-VAX CAMAC links.

In addition to Gould/Sel CAMAC links, TFTRutilizes Micro-Vax CAMAC links as shown in Fig. 1.The Micro-Vax link for the Thomson Scatteringdiagnostic is shown in Fig. 3, and is typical of allTFTR Micro-Vax links. The CCI is a Kinetics 2060serial highway driver. The crates are fiber opticcoupled by Lecroy 5211 U-ports. The link can beoperated bit or byte serial at 5MHz.

TFTR Block Transfer System

The data transfer from the TFTR CAMAC crates to the

Fig. 4 Block Tratnsfer System. This link providesdata acquisition parallel to the CAMAC link,but with approximately 20 times greater

throughput.

TPTR CAMAC Module Family

TFTR CAMAC module capabilities include transientrecordling, timing and sequiencinq, counting and(histogratnming, digital and analog monitor and control,and memory expansion. Th-is family of inodules evolvedbased on the need to support TFTR diagnostic andcontrol systems, and is briefly addressed 'here. Thenumber of TFTR points serviced by these modules issummarized by Table 2.

The data acquisition modules unique to TFTR CAMAC

provide many features: (1) memory that is commnon andexpandable to digitizers, histogramining memorycontrollers, and scalers; (2) remote control of alltiming pulses and time gates; (3) pre- and post-trigger options (digitizers); (4) channel orientedreadout on inm-ltichannel digitizers; (5) block mode-meemory usage for selection of digitizer channel set.s;(6) statu-s registers to deetermine whether thedigitizer is armed, digitizing, or ready for readout;(7) remote memory loading for tests and verification;

OperatorsConsole

972

(8) internal and external clocking and triggering, and

inpujt signal range selection; and (9) there are threespecies of digitizers programmable to sample up to 40

KHz at 12 bits, 500 KHz at 12 bits, and 2 MHz at 8bits.

#87X0298

LC)IoXT

controller (KS3912) and the I/O board (KS2912). A 4Kmailbox memory (KS3821) is used to transfer data

between the LSI and the Gould/Sel host computer. TominimTize overhead and program size, there is nooperating system in the microcomputer and all code is

written in assembly language. The entire program fitsinto 4K words of PROM memory; the remaining 56K of RAMmemnory is for reference profiles andl storage of dlatacollected (during the gas pulse.

#86E00109 Piezoelectric

Valves

2000 4000 6000 8000NUMBER HALFWORDS PER TRANSFER REQUEST

Pig. 5 Block Transfer and CAMAC Link Throuighput.Block Transfer throughpuit approaches 250Kbytes per second compared to approximately12 Kbytes for CAMAC.

Synchronotus timing of CAMAC modu-les is achieved by

dlecoding the central facility event encoded clock thathas been presented on the CAMAC bus P1 line. Timing'nodules recognize the active event codes for whiichthat have been programmed and consequently pro(duce one

micro-second trigger pulses at a preprogrammed delay.These triggers are utilized to start moduiles in theirrespective digitizing, timed gate or timing andsequence functions. The TFTR CAMAC family includesthree distinct timning modu-le types: (1) The timingnodiule which generates preprogrammel trig(gerssynchronous to the central facility clock; (2) thetimed gate modules which generate a preprogranmedpul.se width; and (3) the time base modules whichprovidie serial preprogrammed bursts of variablefrequiency pulses and pulse twidths.

In addition to tri(jgering digitizers, timing modlule-sare designed into CAMAC sys tems that require,sequencirng and cycling of such modules as waveformngenerators, scalers, and histogramming controllers.The waveform generators provide signals to systemsrequiring variable amplitude time-dependent control

characteris-tics such as ramps and step functions. The

scalers are used to count pulses from detectors, such

as charge exchange anodes (measuiring particles of

energy and mass) and x-ray puilse height analyzer Silidetectors (to permit dead-time corrections). The

histogramiTning memaory controller is u-tilizeed to recor(d

and store in memory a frequency of class intervals

suich as energy levels (as in x-ray PHA and neutronspec trol9e try) .

Real and Quasi Real Time Control and Data Acquisition

This sec tion describes a few of inany systemconficjgurations that support CAMAC real and qjuasi realtime applications. The configuration shown in Fig. 6

depicts the CAMAC associated with the control andi data

acquisition of the TFTR gas injection system.4 The

DEC ,SI-1 1/23 microcomputer provides real time control

of gas injectecd into the tokanak torus under closedloop feedhack conditions. ThP interface between theTLSI-11 micro-computer and CAMAC is the auxiliary crate

Fig. 6 Gas Injection System CAMAC. The GasInjection CAMAC system provides real timefeedback control of gas injected into theTFTR torus.

The gas injection programn is initialized when a CAMACdigital ouitput hit (H304) sets an interrupt to theLSI-11. This in turn starts a timed gate moduile(HT305) programmed and wrapped around to trigger itselfas an oscillator and provides the gas system cycleclock, which can be set to any multiple of 2ms. Theoscillator output is connecte(d to a LAM line whichthrough the auxiliary crate controller is recognizedlby the LSI-11 as an interrupt to initiate its residentprogram. Fouir other interrupts are generated by thetiming module so that various checks relating to

tokamak event sequences can he made periodicallybefore the LSI executes portions of its controlprogram. In addition there are various host computercommunications established by using digital input andou-tpuit CAMAC modules that interact wi-th thie aulxiliarycrate controller LAM1 lines.

During an injection sequence the LSI moniitors in real

time the scanning AOC (f1320) nodule feedback signalssuch as plasma density and toruls pressure. It

compares these signals to preprogrammed. referencetables in the LSI, calculates the error, and writes a

new value to the CAMAC analog output module (H321 )every 2ms (or selecterl multiple thereof) dJuring the

injection period. The LSI through its process oF

validity checking also generate.s via tne timed gatenodule a permissive gate that enables thepienzoeletric valve driver to function.

A 32 channel digitizer (H908) with 4K words (H903) perchannel records the Feedlback source signals, fillpressures, and valve driver voltages (during the

lischarge. At the en.l of a pulse, selected (data from

the microcomputer and thie digitizer is displayed in

the TFTR corntrol roomn. All the recorded data are

archived for off-line analysis.

A quasi real time (lata acquisition system is

considered next and shown in Fig. 7. Th1e diagramdepicts the CAMtAC hardware configuration required Lu

Block Transfer J

CAMAC Link

I_IwI

973

monitor up to 512 type E thermocouples on eac'n of theTFTR Neutral Beam Bseamline components. The timing(mo(lule (H404), upon recognizing thie beam fire eventcode fromn the encodled clock signal on the CAMAC crateAataway, triggers the timing and sequencing mo(dule(1H412) synchronously with the power line 60 Hz zerocrossover point. The timing and sequencing modulecontains a preprogramme(d array of 1024 triggers.These pulses cause all 32 MUX's (H359) to index theirchannels and present 32 new signals to the digitizers(H1908). They also trigger the digitizers to samplethe MUX data. The timing and seqtgence array oftriggers consists of one microsecond pulses separatedby 500 microseconds so that the digitizer has enoughtime to sarmple the MUX input. Completion of samplingsets an event which schedules a program to read anddisplay the appropriate waveforms in the TFTR controlroomT.

T.C.S. #86EO013E Type

rooml. Prior to a typical TFTR shot, all CAM4AC moduleswill have been set to user determinel timing valumsand( armed. rJpon receipt of an enco(ied "Start ofDischarge" (TO) signal, the I404A timing fnojule ouitpuitwill trigger the H412 timing and sequencing modlule andienable the H908 transient digitizer modlule. The H412provides output trigger pulses to the spectrum

# 86E0009

- 5 CHANNELS NEUTRONFLUCTUATIONDETECT 18 CHANNELS

-6 CHANNELS SURFACE BARRIERION DENSITY DETECTORS

111111111}11 ,I211111111

18 CHANNELSION DENSITYDETECTORS

MODULE KEY: H404 - TIMING MODULEH4 12 - TIMING AND SEOUENCINGH 911 - SCALERH903 - MEMORY

Fig. 8 Fusion Products Diagnostic. Timing andsequencing data acquisition systemmeasurement of particle specific energy andmass utilizing latching scaler pulse counterand memory storage.

#86EU008

CH C12 CH3 CH4 CH5 CH6 CH7 CH8

Fig. 7 Neutral Beam Temperature Data AcquisitionSystem. This CAMAC system provides quasireal time data acquisition for 512 channelsof thermocouple data per beam line.

The CAt1AC configuration depicted by Figs. 8 and 9represents another TFTR data acquisition system u-sedto implement the Fusion Products dignostic. Thetiming module (H404) recognizes the appropriate eventcode for which it was preprogrammed. It thengenerates a trigger to each timning and sequencingmodule (11412) which in turn generates apreproqrammedarray of one microsecond triggers to activate thelatching scalers (H911) and MUX control for thehistogramming memnory controller (1H356). The scalerscount an(d store in memory the energy level pulsesreceived from the various detector channels. Thehistogramming memory controller receives a wri teaddress strobe along wi th a twenty bit data encodedaddress from equipment external to the module. Themodule resets the "ready for address" flag and datafrom the location addressed in remote memory will beincremented by a value of one. After this step itwill set the ready for input address flag. Thecomplete cycle must be completed in a maximum of twomicroseconds. This example is typical of scaler andhistogramming applications. The data stored1 in memoryis subsequently read by a program via the CAMACdataway or block transfer system and is displayedgraphically in the TFTR con-trol room.

Another application of CAMAC equipment, shown in Fig.10, will he used to sample and digitize the outputs ofspectrtum analyzers in real -time which will receiveMicrowave Scattering signals transmitted over fiberoptic links from the TFTR Hot Cell to the TFTR control

MODULE KEY: H412 - TIMING AND SEQUENCINGH356 - HISTOGRAMMERH903 - MEMORY

Fig. 9 Fusion Products Diagnostic. Timing andseqLuencing data acquisition system utilizinghistogrammer memory controllers to record andstore inmelnory a frequency distribution as afunction of class intervals such as energylevels (as in x-ray PHA and neutronspec tromne try) .

analyzers and to the H904 time base generator. TheH994 is pre-programmed to put out a series of timingpulses whose frequency and number is selected by theexperimenter to match the spectrum analyzersettings. These 1904 pulses will he used as theexternal clock for the H908 module, which will thendigitize the spectruim analyzer ramp outputs andfrequiency analog outputs. The net effect will be touse the H904 modlule as a frequency burst generatorwhich causes the H908 to digitize only when thespectruim analyzers are active. The modules run at aconstant digitizing frequency until the availablememory is filled, or may be delayed to start at aprogrammable timne after TO.

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#87EE00 I 0

Fig. 10 Microwave Scattering diagnostic. Timing andsequencing CAMAC data acquisition system usedto sample and digitize spectrum analyzer datain real time.

Equipment Support, Reliability, and Calibration

Several diagnostic tools have been developed to assistin support of the approximately 5,500 modulesdistributed throughout all the CAMAC systems on TFTR.These tools provide for rapid diagnosis of problems.At the device level, software utility routines permituser-interaction with CAMAC I/O by device definition;device and memory monitoring; and plotting of data anddigitizer testing. Utilities at the computer centralfacility level permit user-interaction with CAMAC I/Oby CNAF; crate initialization; status monitoring; andtranscribe link error codes into literal text. User-interaction directly from the subsystem computer usingCNAFs is also available. At the CAMAC crate and linklevel, control and monitoriing by CNAF using an IBM PCor Compaq in conjunction with a serial highwaydriver also has proven extremely useful. welldefined, and written troubleshooting procedures andtechniques have been developed for both the CAMAC andblock transfer links.

per year time (8,736 hours) gives a component failurerate of only 0.0115 component failures per one millionhours. This is a clear indication that the commercialgrade parts used in the modules are givingperformances comparable to Mil-grade part performance.

Also at TFTR all transient digitizers are routinelyperiodically measured in the field to determine driftperformance. This is a normal function carried out bythe engineering calibration laboratory at Princeton.Modules that have been determinedi to be out ofacceptable specification tolerances are pulled out ofservice, calibrated, and returned to service uponcompletion. Additional module types, such as waveformgenerators DAC's, and AOC's are planne(d to be includedin this process in the near future.

Conclusion

CAMAC and Block Transfer have proven to be reliablesystems with performance and functionality adequatefor data acquisition and real time control of theTFTR. In general CAMAC capability and flexibility todependably support and satisfy system requirements andimplementation has been demonstrated. The indicationsseem to predict that further evaluation over the lifeof TFTR is expected to reveal continued satisfactoryreliability and performance.

References

1. Modular Instrumentation and Digital InterfaceSystem (CAMAC)ANSI/IEEE std. 583-1982.

2. W. A. Rauch, Rev. Sci. Instrum., Vol. 57, No. 8,August 1986, pp. 1898-1900, TFTR CAMAC DataAcquisition System.

3. H. J. Delgatto, and G. J. Bradish, Proceedings ofthe 10th Symposium on Fusion Engineering,Philadelphia, PA, pp. 920-924.

4. M. E. Thompson, H.F. Dylla, P.H. LaMarche, N.D.Arnold, W.A.Rauch, D. Mueller, and R.J. Hawryluk,J. Vac. Sci. Technol. A, Vol. 4, No. 3, May/Ju.n1986, Tokamak Fusion Test Reactor gas injectioncontrol.

An examination into the performance of CAMAC has shownthat reliability overall is good and has especiallyimproved during the last two years (FY86 andi FY87).This we attribute to increased QA workmanshipinspection of all CAMAC components, and a programinitiated at Princeton to upgrade its older CAMACpower supplies with computer grade parts. In additionthe QA department at Princeton is presentlyundertaking a program to compute and predict the mean

time between failures (MTBF) and reliabilityprobability of survival, for each of the next 10years, for certain selected CAMAC modules. Meanwhilean independent snapshot of very closely monitoredCAMAC systems has revealed MTBF 3 to 5 times betterthan the specified 10 year MTBF (i.e., better than the10% per year failure rate). Table 3 shows the failurerates calculate-d for FY85, FY86, and the first halfyear of FY87. Table 3a summaries the annual failurerate percentage for this sample group of approximately500 CAMAC modules spread over several CAMAC systems.Table 3b displays an extrapolation of the data for thetotal population of TFTR modules. In addition to thelow failure rates of only 3% shown in tables 3a and3b, further analysis of the data has indicated a partsfailure of only 1 part in 10,000. Also whenconsidering the number of failed circuit componentsfor FY86 (approximately 150 for this group) divided bythe product of total TFTR CAMAC components(approximately 1.5 million ) and the amount of on-line

*Work3073

supported by U.S. DoE Contract # DE-AC02-76CHO-

CAMAC Link Name

DIAG 1DAIG 2BEAM 1BEAM 2TOK 1TOK 2SAFETYCONSOLE

TOTAL

CAMAC Crates On Line

6046502527381636

298

TABLE 1

CAMAC CRATE SUMMARY

____________DEVICE TYPEAM AC 08l nc TM MO DA SP

76 4572 1392 380207 2160 949 82584 6242 1666 2910 577 0 0

TOTALS 2778 367 13551 4007 1496 108

Legend: AMACDMDC

- analog monitor points- analog control points- digital monitor points- digital control points

TM - timing module pointsMO - motor control pointsDA - data acquisition pointsSP - special points (miscellaneous

such as mailbox memory)

TABLE 2

POINT LIST SUMMARY

NUMBER OF MODULEFAILURES

15219

APPROXIMATENUMBER OF MODULES

ON-LINE

500600660

TABLE 3a

Summary of sample group

of CAMAC module failures

APPROXIMATE TFTRFISCAL TOTAL ON-LINEYEAR MODULES

FY85FY86

1/2 FY87

500052505500

SAMPLEX FAILURE

X

X

X

APPROXIMATE= TOTAL NUMBER

OF FAILURES

0.030.030.03

150158165

TABLE 3b

Summary of TFTR CAMAC module failures

TABLE 3

Summary of FY85, FY86 and 1/2 FY87CAMAC module failures

CAMACLINK

DIAG 1 &2BEAM 1&2TOK 1 &2SAFETY

7111 30371945

975

307260

88914931 49

0

83010

3531 84

FISCALYEAR

FY85FY86

1/2 FY87

ANIJANLIZEDFAILUJRE

3.0%3.5%2.7%