IEEE Transactions on Nuclear Science, Vol. NS-34, No. 4, August 1987
The VALET-Plus, a VMEbus based microcomputerfor Physics applications
Tim Berners-Lee, Christopher Parkman, Yves PerrinJorgen Petersen, Louis Tremblet
Data Handling Division - CERN1211 GENEVA 23 - Switzerland
Abstract
The VALET-Plus is a modular VMEbus based microcomputer system developed at CERN for use inapplications such as the development and testing of electronics, equipment control and data acquisition. Firstreleased in 1985, more than 100 VALET-Plus systems are used today in 14 countries. The system will be describedwith particular emphasis on the SPIDER data acquisition package which offers both real time programming, usingan interactive language, and fast data collection at rates ofmore than 1000 formatted events per second.
INTRODUCTION
The VALET-Plus is a modular VMEbus basedmicrocomputer system developed at CERN for use inthe development and testing of electronics, equipmentcontrol and data acquisition. One of its originaldesign goals was to provide a common tool for testingelectronics developed by institutes collaborating inlarge experiments at the CERN SPS, PS/LEAR andLEP accelerators.
inconvenience. Use of an Ethernet connection to amini (or personal) computer further reduces thislimitation and gives access to other file bases.
PeripheralServer
The VALET-Plus consists of two computer systemsloosely coupled via a standard link as shown in Fig.1 .On the one side, the VALET provides an optimisedenvironment for connection to the "Physics" buses andon the other side, a (personal) computer acts as aninexpensive peripheral server and provides the userinterface.
The application software and libraries execute in aVMEbus M68000 processor which has direct control ofthe VMEbus, CAMAC, FASTBUS, GPIB, high speeddata recording devices and of the Ethernet LAN.Physics data input and output are, thereby, madedirectly with minimum overhead.
A (personal) computer connected to the VALETvia a standard communication link (at present RS-232C or Ethernet) provides both support for standardperipherals such as keyboard, screen, printer, anddisk, as well as the interface to control the VMEbusbased application processor. These services areprovided, in a user transparent way, by means ofRemote Procedure Calls (RPC) [13]. The firmwarerunning in the VMEbus M68000 is independent of thetype of computer chosen. The communicationsoftware ("BRIDGE") in the connected computer iswritten in Pascal and is, to a large extent, portable. RS-232 has been chosen, despite its bandwidth limitation,in order to minimize restrictions on the user's choiceof computer. Since little test application software is diskintensive, the bandwidth limit of RS-232C is rarely an
. Server of standardperipherals
. User interface* Low cost
* Executes the application. Based on commercialmodular system
. Efficient Physics 1/0* Fast data recording
V-ALET
Physics 1/0
Systems loosely coupled
via a standard link
Fig. 1: The VALET-Plus concept
THEHARDWARE
The VALET-Plus is entirely based oncommercially available hardware from a number ofmanufacturers. This approach takes advantage of thecompetition in the VMEbus and personal computermarkets and it leaves considerable freedom to both theimplementors and the users in the evolution of thesystem.
As shown in Fig.2, the VALET itselfconsists of [21:
- AVMEbus crate fully equipped with adequate powersupplies and cooling
- Three mandatory VMEbus modules:
The Motorola MVME101 processor moduleAn EPROM module with a minimum capacity of512 kbytes (from a list ofrecommendations)ADRAM module with a minimum capacity of1 Mbyte (from a list ofrecommendations)
- Optional VMEbus modules:
CAMAC Branch Driver: CES 8210(+ DMA option)
.FASTBUS:Antares/Struck STR302(includes DMA)This module is able to drive the FIORI, CFI andFast Sequencer FASTBUS masters.
. GPIB (IEEE-488): Motorola MVME300(includes DMA)
. COLOUR GRAPHICS controller: Eltec GRAZ
. SCSI interface: Compcontrol CC-74
. ETHERNET: LRT Filtabyte 25.1
IBM-PC HP- 200
FASTBUS
Fig. 2: The VALET-Plus architecture
THE SOFTWARE INTUE VALET
All software modules in the VALET and the tools tcdevelop programs to be executed in the VALET-Plus arebased on CERN standard software packages supportedindependently from VALET-Plus. Unless mentionedas written in PILS, all the software modules describedbelow areROM based in the VALET.
MoniCa
MoniCa [11] is a debug monitor for the M68000microprocessor family. It provides run time supportfor Assembler and higher level languages such as C.Fortran, Modula-2 and Pascal. Powerful debuggingaids are available. A logical channel concept andinterrupt driven input/output operations areimplemented. MoniCa is written in Assembler andPascal and is in widespread use at CERN.
PILS, (a Portable Interactive Language System) [31Jis designed to improve the portability of applicationsoftware and programming environment. It has beeninstalled with identical application libraries on VAXand M68000 based systems. PILS contains ANSIMinimal BASIC as a subset, but it provides additionalfeatures such as data types, modules, controlstructures, subroutines and functions withparameters which create a more powerful languageand distinguish PILS from some other interactivelanguages. A compiler, built into the PILS system.allows improved execution speed whilst retaining theinteractivity and is presently available for the VAXand the M68000. The compilation is made entirely inmemory (it does not access disk files) and is thereforefast.
The Application Libraries
Standard libranres also available on VAXNORD systems are installed with PILS:
Additional libraries have been implementedspecifically on VALET-Plus as described below:
VMEbus Specific Routn.
This is set of library routines providing singleand block access to physical memory as byte, wordor long word cycles. These simple routines areincluded to allow convenient testing anddebugging ofVMEbus modules from PILS.
M68000 Specific Routine
Routines to associate a M68000 exception vectorwith a user subroutine such that the subroutine isscheduled on occurence of the exception. Theseroutines are particularly useful in real timeapplications and to develop drivers.
GPIB (IEEE 488) librarY
A library is available for the Motorola MVME300module, which has DMA transfer rates ofup to 500kbytes/sec. It is written as a PILS module and ituses theVMEbus library mentioned above.
SCSI libra
A library with the necessary primitives to drivedevices interfaced to the SCSI is available.
Magnetic Tape (MT) and Quarter Inch CartridgeIC) librah
Libraries with identical external specificationshave been implemented to support reel-to-reel andQIC tape drives interfaced via SCSI. Theselibraries are written as PILS modules using theSCSI library mentioned above.
Timer library
Routines to control the hardware timer chippresent on the VALET CPU module. Associationof timer interrupts with a user subroutine ispossible.
THE COMMUNICATION FACILITIES
VALET-Plus offers several possibilities forcommunication with other computers. The VALETpersonal computer / terminal may be used as a remoteterminal of a host system connected via RS-232 to thesecond serial port of the CPU module. For filehandling, the services provided include the access toASCII files from PILS statements and commands,Motorola S-records downloading into the VALET andfile copy operations between file bases. File access isbased on layer 2 (file management) of the PILS HostInterface (PHI). The implementation uses RemoteProcedure Calls (RPC) [13]. The medium can be aserial line or an Ethernet link. For RS-232, a simple ad-hoc protocol was developed. In the case of Ethernet,messages are transferred over raw Ethernet. Time-outand errors are reported but, at present, no errorrecovery or retry mechanism is provided. Forinstallations with a CAMAC link to CERNET [9], aMoniCa command permits downloading of absoluteprograms into the VALET processor from anyCERNET host. A utility program handles ASCII filetransfers between the personal computer disc and anyCERNET host.
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IHE SOFTWARE INTHE PERSONAL COMPUTIERThe BRIDGE is the utility program which allows tie
personal computer to act as a terminal emulator aind aserver of the remote procedure calls sent from theVALET as shown in Fig.3.
The (personal) computer may also be programmedto provide special user interface features such asmenus, windows, etc. depending on the specific type ofmachine.
Implementation PI RU timeon a single CPU PILS (Pieace)Hstsem
system File
Remote procedureceals ---Software independent + Software written in
of personal computer Terminal traffic PASCAL
Fig. 3: The interface between the VALET and itsperipheral server
The remote procedure calls are oftwo kinds:
File management requests issued by the 'local PHI"in the VALET's M68000 and served by acorresponding "Remote PHI" in the personalcomputer BRIDGE.
Graphics requests containing records of the "capturefile" issued by the VALET graphics library to beinterpreted and plotted on the personal computerscreen.
The BRIDGE has been written in PASCAL forportability. System specific code such as control of theserial port, file and graphic management is wellisolated to ease adaptation between implementations.
The BRIDGE utility has been installed on the following(personal) computers:
Apple MacintoshApple Lisa (MacXL)IBM-PC /MS-DOS and compatiblesHewlett Packard 200/300 SeriesVAX/VMS
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PROGRAMMING INLANGUAGES OTHERTHAN PILS
Though primarily offered as a PILS machine,VALET-Plus can be programmed in other languagesby means of a suite of cross-software. The CERN cross-software for the M68000 family [10] includesAssembler, PASCAL, FORTRAN 77, C andMODULA_2. With the exception of the FORTRAN 77and C compilers, the cross-software is written inPASCAL. The compilers generate a commonrelocatable format (CUFOM) [12] for which link editorsand loaders exist. The output of this chain is anabsolute image of the program represented as an ASCIIfile of S-records, which can be loaded by the VALET'sdebug monitor MoniCa. The cross-software isavailable under VAX/UNIX-BSD4.2, VAX/VMS,IBM/MVS and on several other minicomputers andmainframes. When substantial non-PILS programdevelopment is required, the cross-software should beinstalled, if possible, on the local personal computer(having good hard-disc support). It has been installedon the HP200 family under the PASCAL Work StationSystem PWS (with the exception of the cross FORTRANand C compilers). A command file allows users to linkFORTRAN programs to the libraries which areresident in the VALET EPROM. This reduces thenumber of S-records, and therefore the load timerequired for programs which make extensive use oflibraries.
REAL TIME PROGRAMMING
PILS allows run-time access to subroutineaddresses and provides a compiler which generatesreentrant code. These features have made real timeprogramming in PILS possible. Standard librarycalls (e.g. CCLNK for CAMAC) have beenimplemented together with corresponding interrupt"dispatchers" to permit the association of an externaltrigger (e.g. a CAMAC LAM) with the execution of auser"event" subroutine.
SPIDER
A simple modular data acquisition package,called SPIDER (Simple Portable Interactive Dataacquisition EnviRonment) has been developed for theVALET-Plus. It provides the user with a circular buffermanager, event formatting and optional datarecording on MT or QIC drives interfaced via the SCSIbus. It is written in PILS and enables the user to writethe monitor program and event read-out routines in thatsame interactive language. Its modular structure andwell defined interfaces, shown in Fig.4, are such thatdevelopment of a new producer or consumer is easy.With the 8 MHz M68000 processor at present used in theVALET-Plus, SPIDER can collect more than 1000formatted events per second. The relative executionpriority of the competing "processes", which wouldnormally be handled by the operating system in areal multi-tasking environment, had to be provided by
some other means on the VALET-Plus under MoniCa.Since the competing "processes" (PILS subroutines)are interrupt driven, the hardware interrupt levelpriority mechanism is used and the library associatedwith the trigger bus has been complemented withroutines to allow blocking of interrupts whenever a lowpriority process requires protection (access to globalvariables, buffer full whilst high priority analysis isselected, etc).
The buffer manager controls the data flow through acircular buffer, the characteristics of which (numberand size of sub-buffers), are defined by the user. Itsupports one input process (producer) and two outputprocesses (consumers) for analysis and datarecording. The relative priority between the input andthe analysis is selected at start of run.
Fig. 4: The structure ofSPIDER
Input is interrupt driven. User subroutineswritten in PILS and compiled are executed on theoccurence of a trigger. At present, triggers can onlyoriginate from CAMAC, but support for other sourcesshould be relatively easy. There is an option to replay arun, in which case the input is made from the datarecording device.
A set of subroutines permit the program to startand stop data acquisition runs and to retrieve eventsasynchronously from the circular buffer into a userarray. Runs are automatically ended whenever therecording device reaches the end of media or hits anunrecoverable parity error.
Data recording is an option selected at start of run.It is performed automatically (transparently to theuser) and concurrently with data taking andanalysis. Events and records are formatted according
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to the CERN EPIO specification [14]. At present, datacan be recorded either on MT or on QIC drives. Theindependence of the buffer manager from datarecording device specific libraries has been achieved byintroducing an extra layer of identical high levelsubroutines for every possible recording "consumer".
SPIDER is easy to use because of its modularityand simplicity (interactive language and standardlibraries). Further help is provided by the availabilityof a skeleton monitor program, examples of user eventread-out routines, command files as well as SPIDERcontrol and status subroutines to ease debugging. Thispackage has been successfully used, on a trial basis, bythe UA2 experiment at CERN during the Autumn of1986. It will be officially released in May 1987.
DEVELOPMENTS
Developments will continue mainly in thefollowing directions:
. Integration of new hardware products to improveperformance and flexibility of the system and toreflect the market evolution (e.g. M68020 processor,M68881 floating point co-processor)Generalization of the use of remote procedure calls toall services provided by the peripheral server (e.g.terminal traffic)Generalization of the use of Ethernet / Cheapernet tolink to systems other thanVAX (e.g. IBM-PC).Study of the feasability of porting the VALET softwareto a multi-tasking operating system (e.g. OS9/68K orRMS68K)Integration of VALET as on-line test / spy / pre-processor system into multi-processor read outsystems. This implies investigation on processor toprocessor communication, synchronization andarbitration, resource management, alternate datapaths (e.g. VSB).
The use of shared memories and mailbox interrupts byseveral SPIDER applications running in connectionwith each other might be a basis for parallel acquisition,event filtering and event building applications.
STATUS
First released in 1985, more than 100 VALET-Plussystems are used today by scientific laboratories andinstitutes in 14 countries. Most systems incorporate anAPPLE Macintosh or an IBM-PC; a few systems useVAX, HP200 or APPLE Lisa. A complete set ofdocumentation [1,2,3,4,5,6,7,11] is available on a self-help basis on CERN IBM WYLBUR service. AVALETNEWS scheme based on Electronic mail hasalso been implemented to communicate with the usercommunity. Interest in the concept have also resultedin implementations on other M68000/MoniCa baseddesigns such as the FASTBUS General Purpose Master(GPM) by the DELPHI collaboration and on the
CAMAC "Controlleur de Branche d'Acquisition"(CBA) by the OPAL collaboration and it is being done onthe CERN Host Interface (CHI).
CONCLUSIONS
Originally developed as a simple test system, theVALET-Plus has become, through three firmwareupgrades, an efficient data acquisition system withfeatures such as compiled PILS, real time facilities andsupport of data recording devices. The choice ofarchitecture and standard basic hardware andsoftware components have made this evolution smoothand leaves openings for new developments.
ACKNOWLEDGEMENTS
We wish to thank P.Scharff-Hansen who greatlycontributed to the original specification and to thelaunching of the VALET-Plus project, H.von Eickenand R.Nierhaus for their help with MoniCa andgraphics respectively, the DD-SW group for their supportin cross software matters and C.Mazzari for his helpwith administration and user support.We, also, want tothank D.Sendall, E.Rimmer and A.Bogaerts for theirencouragement and advice.
REFERENCES
1. VALET-Plus Operations GuideOC GROUP - GA/MAN7 CERN Data Handling Division.
2. VALET-Plus Hardware GuideOC GROUP - GA/MAN6 CERN Data Handling Division.
3. PILS Reference ManualR.D.Russell, L.Tremblet, D.O.WilliamsOCGROUP - GEN/MAN2 CERN Data Handling Division.
4. Standard CAMAC SubroutinesOC GROUP - GEN/MAN5 CERN Data Handling Division.
5. Users Guide to CERNFASTBUS RoutinesOCGROUP - CERN Data Handling Division.
6. MINI Common Histogramming LibraryOC GROUP - GENAMAN8 CERN Data Handling Division.
