MODASC is an ASIC that performs wide area mobile data acquisition using satellite communication to provide global coverage. This circuit provides two operation modes: an autonomous mode, that periodically establishes connection with the control center, and a slave mode, working as a peripheral connected to a general purpose micro controller. This experiment has been realized under FUSE special action in collaboration with SAINSEL

García Franquelo, Leopoldo

García Ortega, Juan de la Cruz

Janer Jiménez, Carlos

López, J.

Marín, F.

Quero Reboul, José Manuel

Toral, S. L.

idUS. Depósito de Investigación Universidad de Sevilla

MODASC: ASIC for Mobile Data Acquisition Systemsusing Satellite CommunicationsJ.M. Quero, L.G. Franquelo, C.L. Janer, J.G. Ortega and S. ToralDpto. de IngenierÂõa Electr ÂonicaEscuela Superior de Ingenieros,Avda. Reina Mercedes s/n, Sevilla±41012 (SPAIN)Tel.: +34 (9)5 455 68 57Fax: +34 (9)5 455 68 49e±mail: toral@gte.esi.us.esF. MarÂõn and J. LÂopezSAINSELManuel Velasco Pando s/n, Sevilla (SPAIN)Tel.: +34 (9)5 457 36 91Fax: +34 (9)5 457 93 62AbstractÐ MODASC is an ASIC that performs wide area mobile dataacquisition using satellitecommunication to provide global coverage.This circuit provides two operation modes: an autonomous mode, thatperiodically establishesconnection with the control center, and a slavemode, working as a peripheral connected to a general purpose microcontroller. This experiment has been realized under FUSE specialaction in collaboration with SAINSEL.I. INTRODUCTIONMost data acquisition systems make use of com-munication channels to send captured data to thecontrol center. These communication channelsare usually radio links, local computer networksor dedicated telephone lines. The selection ofthe most suitable communication channel is deter-mined by taking into account application parame-ters, such as distance, installation and transmissioncosts, liability,: : :All previously mentioned com-munication channel alternatives are used for ®xedinstallations or mobile stations in a local area. Butwhen wide area data acquisition is required, satel-lite communication is the most valid alternativebecause it provides global coverage.In this paper we present an ASIC designed toacquire data and send it to a control center viaInmarsat. This circuit provides two operationmodes: an autonomous mode, that periodically es-tablishes connection with the control center, and aslave mode, working as a peripheral connected to ageneral purpose microcontroller.II. FUNCTIONAL DESCRIPTIONThe functionality of this circuit can be summarizedas remote data acquisition and communication us-ing satellite links.As it has been mentioned above, this circuit presenttwo different operation modes: an autonomousmode and a slave mode.In the ®rst mode, the circuit uses the Data Com-munication Equipment (DTE) GALAXY-C/GPSfrom TRIMBLE [1]. This transceiver uses InmarsatStandard-C satellite communication protocol andalso receives signal according to GPS standard.The DTE/ASIC physical interface is over an RS-232 link.In the second mode, this connection and its pro-tocol are no longer needed, although they can beeasily implemented using one of the 5 availableserial channels implemented in MODASC.The mode selection is determined by pin namedCONFIG, where 0 and 1 indicates autonomous andslave modes respectively. As both modes are in-dependent, bellow they are explained in differentsections.A. Autonomous ModeIn this mode MODASC captures environmen-tal data and also determines its position usingGPS. According to a predetermined schedule,MODASC waits until the control center establishesa connection, sending queries to determine ASICpresent status.In ®gure 1 a block diagram of autonomous modeis shown. In this mode, the most critical issue isto ensure power supply to guarantee proper op-eration and location of the system. Therefore, en-ergy consumption minimization should be taken.MODASC internally stores sensor information andreceives GPS position from the transceiver. All thisdata is periodically sent to the control center.The functionality of the circuit is completed withTRANSCEPTORCADCONTROLCADCAD NBATRS-232-CLD1LD2SETTTRA1 SETTRA2MAEBUZSETFLSHCONFIG=0SNAP....NBATPOSITIONSPEEDCOURSEREALTIMECLOCKTRANSCEPTOR         CRCDESCOMMUNICATIONFREQUENCYDIVIDERPOWERSUPPLYCONTROLPROTOCOLARITMETICUNITMEMORYSENSORSENSOR MEASUREMEASUREEPROMMEMORYRAMADDRESS BUSDATA BUSBLOCKSURVEILLANCEANTENNAFigure 1: ASIC functional diagram in autonomous modeviolation sensors, optical and acoustical signals toindicate functional status, control block, arithmeticunit, frequency divider and internal con®gurationregisters.MODASC isconnected to the GALAXY transceiver using RS-232-C. In order to achieve maximum compatibil-ity with other transceivers, the communication be-tween ASIC and GALAXY utilizes STANDARD-CInmarsat Protocol when possible. The Communi-cation Module is devoted to this communicationprotocol.To achieve data privacy, standard encryption al-gorithm (DES)[2] is implemented in MODASC. Toverify data integrity, CRC code is added at the endof every message.The Power Supply Module deals with power con-sumption, activating peripherals only when it isneeded. The activation schedule can be deter-mined using programmable timers. This mod-ule also supervises battery voltage level. Whenthis voltage level is bellow a prede®ned reference(50%), MODASC begins working in energy savingmode. When in this mode, its functionality is re-duced to provide communication with the controlcenter.The Analog Signal Acquisition Module capturesenvironmental analog data. Eight ten-bit analog todigital stochastic converters [3] are implemented.The main advantage of these converters is that usepurely digital technology, thus decreasing manu-facturing costs.A real-time clock is included to determine commu-nication periods. This clock is update wheneverASIC receives GPS time.The Global Control Module determines the globalfunctionality of the system, including access to sys-tem buses.The kind of messages used in INMARSAT-C pro-tocol is the 'Store & Forward' class, chosen becauseof its high reliability and acceptable transmissioncost.For debugging facilities, an auxiliary serial port isconnected to the serial port devoted to transceivercommunication, as it is shown in ®gure 2. Thisway, when CONFIG is equal to 0 (autonomousmode), the auxiliary serial port receives all mes-sages that are transmitted between transceiverand ASIC, and it can directly send data to thetransceiver to be con®gured. In slave mode (CON-UART2UART1GALAXY(TRIMBLE)TERMINALCONFIGCONFIG0101ASIC0RS-232-CRS-232-CADAPTERADAPTERFigure 2: ASIC-Transceiver protocol monitoring in autonomous modeFIG=1) serial ports are working independently.B. Slave ModeIn this mode MODASC works as a peripheral to astandard microprocessor. In ®gure 3 a block dia-gram corresponding to the slave mode is shown.An 8-bit data bus, 6-bit address bus, R= W and CSare microcontroller's signals to access ASIC data.In this mode, MODASC provides 5 serial commu-C A/D C A/D C A/D C A/DCanal 0Canal 1Canal 2Canal 4Canal 3RxD0TxD0RxD1TxD1RxD2TxD2RxD3TxD3TxD4RxD4Rec. BufferTransm. BufferRec. BufferTransm. BufferRec. BufferTransm. BufferRec. BufferTransm. BufferRec. BufferTransm. BufferWatch - DogWDC A/D C A/D C A/D C A/DrelojProgramacionR/WED7ED5ED6ED4ED3ED2ED1ED0SD7SD5SD6SD4SD3SD1SD0WDRESETSD2ECA7SE7 SE6 ECA6 SE5 ECA5 ECA4 ECA3SE4 SE3 SE2 ECA2 ECA1SE1 SE0 ECA0ADB 5:0DB 7:0CSINTSCLSDAI2CRDDRDIclave DESDATA BUSADDRESS BUSREGISTERSSTATUS AND MASK CONFIGURATIONREGISTERSSTATUSMASKSREAL TIME CLOCKBAUD RATEGENERATORIRQ INTERRUPTCONTROLLERFigure 3: ASIC functional diagram in slave modenication ports. They manage 8 data, one start andone stop bits. Whenever an UART receives onedata byte, it generates an external interruption.Similarly, when one data byte is written in thetransmission register, it is automatically transmit-ted. When this buffer empties, the correspondingstate ¯ag is activated. There exist a mask registerto deactivate interruptions, and an error register toindicate frame errors.Another communication block implements a sim-pli®ed version of an I2C bus [4]. This is a syn-chronous serial communication channel, that uti-lizes only two lines: a bidirectional data line anda synchronization clock line. In our approach, thismode is considered to be master respect to periph-eral circuits that work as slaves when they are con-nected to this port.Communication frames are composed of 7-bit ad-dress, a R/W bit, one byte of data, and an receptionacknowledge bit (see ®gure 4). The synchroniza-tion clock frequency is 100 K bits/s.SDASCL1 2 7 8 9ACKAcknoeledgement1 2 3 7 8 9AcknoeledgementSTOPSTARTFigure 4: I2C bus data transferSignal timing and electrical features comply spec-i®cations given in [4].External control of I2C bus is realized by writingand reading operations of corresponding outputand input data registers. Available status registerallows for control of this block. Both interrupt andpolling management of this port is possible.A Watch-Dog circuit has been included in ASICfunctionality to prevent microcontroller from be-ing blocked.ASIC functionality is completed with 8 input and8 output digital signals, 8 Analog to digital con-verters based on stochastic logic [3] as it is drawnin ®gure 5, a real time clock, and DES blockVoViASICSUCESIVEREGISTERAPPROXIMATIONDIGITAL VALUERANDOM NUMBER GENERATORCDEFigure 5: Block Diagram of an analog to digital converter based onstochastic logicIII. IMPLEMENTATIONCritical blocks, such as Inmarsat-C protocol, havebeen simulated in C language. Now, the holesystem its being described in behavioral language(VERILOG [5]). The ASIC will be designed usingCADENCE DESIGN FRAMEWORK II. The ASIChas a estimated area of 50mm2 using ES2 ECPD07Standar Cell technology and PLCC-84 package hasbeen selected.REFERENCES[1] GALAXY-C/GPS Users Manual. TRIMBLE. 1995[2] A.S. Tannenbaum Computer Networks. Prentice-Hall Interna-tional. 1989.[3] J.G. Ortega, C.L. Janer, J.M. Quero and L.G. Franquelo. ªAnalogto Digital and Digital to Analog Conversion Based on StochasticLogicº. Proceedings IECON'95.[4] Philips Semiconductors 80C51-Based 8-Bit Microcontrollers[5] Verilog-XL. Reference Manual, vol 1,2,3. Cadence Design Systems,Inc.

MODASC: ASIC for mobile data acquisition systems using satellite communications

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MODASC: ASIC for mobile data acquisition systems using satellite communications

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