3
IEEE Ttavnactions on NuLcteaA Science, VoZ.NS-22, FebtuaL 1975 A CAXAC SERIAL HIGHWAY UTILIZING A LASER LIi4K* C. C. Scaief, III and G. L. Troyer Atlantic Richfield Hlanford Company Richland, Washington 9)352 SUMMIARY A systerm for extending a CAItAC serial highway to a distance of 2 kilometers using an optical link is described. The systerm utilizes cormmercially avail- able laser transceivers operatinq in the pulse mode. Information is transmitted asynchronously and then resynchronized at the receiver interface. The serial highway extension provides effective remote instrunient control and interprocessor communication for routine laboratory analyses and process support. I HTRODUCT IONl 'Atlantic Richfield Hanford Company maintains twio semi-independent analytical laboratories for local process control. The facilities are separated by 2 kilometers (km.) with little automiation and data base support. Each facility does have small dedi- cated computers limited to specific applications with one facility developing CAMAC control. The extension of the existing CAIAC system to the second laboratory will provide interprocessor communica- tion as well as equitable automatic analytical instrument control for both facilities. The recent introduction of the CAI`Ai'tC serial specif- icationl has made the automation and control of rem.ote equipmient attractive and feasible. The elimination of specialized and non-compatible tech- niques to allow conticuous operations wliithin CA,AC at extremely reriote sites is attractive from an end user viewpoint. A laser communication link wias selected to provide a simple direct intertie of remote facilities throunh an extended CACIAC Serial Hlighway (SHF). The systen can provide capability for reliable, hinh speed, cost effective, line-of-sight communications over interpmediate distances of 1 to 30 kilometers (km). SYSTEi OVERVIEWI, For some time, a method of data colmmunication bet- vween the laboratories not dependent on normal slow telephone lines or hinh cost direct wire/moden has been souqht. Such a system should be simple in con- cept to assure straightforward operation, be modular to allowi easy maintenance, allow data rates coniparable to the CAMIC system, and have the majority of components readily available. Usinn the CA;AC serial specification as a base, a systemn has been developed usine a CAIiAC serial driver module, a pair of infra-re(d laser diode transmitter/receiver modules and a siu-lple user designed undefined port2 interface in Ch1,C as shown in block diagram in Fioure 1. The existing CA,AC system is supported by a Data General Corporation NOVA 840 with 40 K of 16 bit nmer,ory. Peripherals on the system include a 1.25 ,i-word moving head disc, twio time share telephone ports, and a bacliground console. All hardwiare applications interfacinn other thian the above is pro- vided with CAMlAC utilizi ng the GEC Elliot Corpora- tion CA,tMAC Executive System. Laboratory equippment interfaced or in progress include chemical titrators, gamma and alpha energy analysis systems, an emission spectrometer, and a mass spectrometer system.. The latter two systermis are located in the second labora- tory, each system with dedicated and limited pro- cessor support. SERIAL DRIVER The CAHAC Serial Driver (SD) is a Kinetics Systenm ,lodel 3992 configured as a normal three width CAilAC module addressable in all specified modes fromi the dataway. This module provides for serial operations wqithin the normal parallel CA'lAC system, without delaying high speed parallel operations and without requiring additional software drivers and interface port. The unit is capable of operating from select- able stepped crystal timie base or variable oscilla- tor frequencies. Operation is performed by loading appropriate data and command registers. A write operation is initi- ated by loading the command register and then the data register. A read is initiated by loading a read commiand, waiting until the transmission is com- plete and then reading the data register. Success- ive reads rm,ay be initiated when the data register is read. The SD is provided with a look-at-me (LA,I) status register, a serial highway status register and a LAM miask register. Proper use of these registers permits low softvware overhead while miaintaining the lovw-error integrity sought in the serial specifica- tions1. LASER EQUIP lENT The laser equipment used is the Amierican Laser Systems 'lodel 736 based on an infra-red solid state laser diode emLittin(g at 904 nanometers (nn) and operated in a pulsed mode. This equipiiient when i-latched with a filtered optical system. and an ava- lanche phototransistor is normally used for line of sinht voice communication up to 30 km. The standard version is rated at a maximum of 10 kilohertz (KHiz) with a pulse vwidth of 100 nanoseconds (ns). The rmaximiurm data rate of the system is rainly depen- dent on the duty rate of the laser diode. A 10 kHz version was used for initial testing and evaluation. A t this (late, a diode configured as a syri,mmetrical optical cavity capable of 1 miegahertz (.,ziz) is being tested. Due to the pulsed operation of the laser, the systew is directly cor;patible with digital systenis and dinital data transfer. Further, the systerm is ,odular with transmitter (XAlT.') and receiver (RCVR) in separate srall enclosures. 499 ARH-SA-1 99 *;'ork perforriled under Contract AT(45-1)-2130, U. S. Atomic Energy Comlission.

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Page 1: A CAMAC Serial Highway Utilizing a Laser Link

IEEE Ttavnactions on NuLcteaA Science, VoZ.NS-22, FebtuaL 1975

A CAXAC SERIAL HIGHWAY UTILIZINGA LASER LIi4K*

C. C. Scaief, III and G. L. Troyer

Atlantic Richfield Hlanford CompanyRichland, Washington 9)352

SUMMIARY

A systerm for extending a CAItAC serial highway to adistance of 2 kilometers using an optical link isdescribed. The systerm utilizes cormmercially avail-able laser transceivers operatinq in the pulse mode.Information is transmitted asynchronously and thenresynchronized at the receiver interface. Theserial highway extension provides effective remoteinstrunient control and interprocessor communicationfor routine laboratory analyses and process support.

I HTRODUCT IONl

'Atlantic Richfield Hanford Company maintains twiosemi-independent analytical laboratories for localprocess control. The facilities are separated by2 kilometers (km.) with little automiation and database support. Each facility does have small dedi-cated computers limited to specific applicationswith one facility developing CAMAC control. Theextension of the existing CAIAC system to the secondlaboratory will provide interprocessor communica-tion as well as equitable automatic analyticalinstrument control for both facilities.

The recent introduction of the CAI`Ai'tC serial specif-icationl has made the automation and control ofrem.ote equipmient attractive and feasible. Theelimination of specialized and non-compatible tech-niques to allow conticuous operations wliithin CA,ACat extremely reriote sites is attractive from an enduser viewpoint.

A laser communication link wias selected to providea simple direct intertie of remote facilitiesthrounh an extended CACIAC Serial Hlighway (SHF). Thesysten can provide capability for reliable, hinhspeed, cost effective, line-of-sight communicationsover interpmediate distances of 1 to 30 kilometers(km).

SYSTEi OVERVIEWI,

For some time, a method of data colmmunication bet-vween the laboratories not dependent on normal slowtelephone lines or hinh cost direct wire/moden hasbeen souqht. Such a system should be simple in con-cept to assure straightforward operation, bemodular to allowi easy maintenance, allow data ratesconiparable to the CAMIC system, and have themajority of components readily available. Usinn theCA;AC serial specification as a base, a systemn hasbeen developed usine a CAIiAC serial driver module,a pair of infra-re(d laser diode transmitter/receivermodules and a siu-lple user designed undefined port2interface in Ch1,C as shown in block diagram inFioure 1.

The existing CA,AC system is supported by a DataGeneral Corporation NOVA 840 with 40 K of 16 bitnmer,ory. Peripherals on the system include a 1.25,i-word moving head disc, twio time share telephoneports, and a bacliground console. All hardwiare

applications interfacinn other thian the above is pro-vided with CAMlAC utilizi ng the GEC Elliot Corpora-tion CA,tMAC Executive System. Laboratory equippmentinterfaced or in progress include chemical titrators,gamma and alpha energy analysis systems, an emissionspectrometer, and a mass spectrometer system.. Thelatter two systermis are located in the second labora-tory, each system with dedicated and limited pro-cessor support.

SERIAL DRIVER

The CAHAC Serial Driver (SD) is a Kinetics Systenm,lodel 3992 configured as a normal three width CAilACmodule addressable in all specified modes fromi thedataway. This module provides for serial operationswqithin the normal parallel CA'lAC system, withoutdelaying high speed parallel operations and withoutrequiring additional software drivers and interfaceport. The unit is capable of operating from select-able stepped crystal timie base or variable oscilla-tor frequencies.

Operation is performed by loading appropriate dataand command registers. A write operation is initi-ated by loading the command register and then thedata register. A read is initiated by loading aread commiand, waiting until the transmission is com-plete and then reading the data register. Success-ive reads rm,ay be initiated when the data register isread.

The SD is provided with a look-at-me (LA,I) statusregister, a serial highway status register and aLAM miask register. Proper use of these registerspermits low softvware overhead while miaintaining thelovw-error integrity sought in the serial specifica-tions1.

LASER EQUIP lENT

The laser equipment used is the Amierican LaserSystems 'lodel 736 based on an infra-red solid statelaser diode emLittin(g at 904 nanometers (nn) andoperated in a pulsed mode. This equipiiient wheni-latched with a filtered optical system. and an ava-lanche phototransistor is normally used for line ofsinht voice communication up to 30 km. The standardversion is rated at a maximum of 10 kilohertz (KHiz)with a pulse vwidth of 100 nanoseconds (ns).

The rmaximiurm data rate of the system is rainly depen-dent on the duty rate of the laser diode. A 10 kHzversion was used for initial testing and evaluation.At this (late, a diode configured as a syri,mmetricaloptical cavity capable of 1 miegahertz (.,ziz) is beingtested.

Due to the pulsed operation of the laser, the systewis directly cor;patible with digital systenis anddinital data transfer. Further, the systerm is,odular with transmitter (XAlT.') and receiver (RCVR)in separate srall enclosures.

499

ARH-SA-1 99

*;'ork perforriled under Contract AT(45-1)-2130, U. S. Atomic Energy Comlission.

Page 2: A CAMAC Serial Highway Utilizing a Laser Link

The XA1TR requires a digital signal input and is edgetriagered with a positive going pulse havinn a rise-time of less than 100 ns. The laser charging cir-cuit supplies approximately 5 micro amps of currentdurino the laser pulse. Energy ermitted at theoptical output is approximrately .2 microjoules perpulse. Operation within the limnits of the cir-cuitry and optics rmakes the laser Class J3.

The RCVR is actuated by detecting energy which haspassed through its optical bandpass filter. Thefilter is designed for the maximum transmission wave-length of 904 nm with a bandpass of 15 nnm. inimqumdetectable signal is 0.5 nanowatts.

Both the XMTR and RCVR have camnera lens optics of50 mm in diameter, 135 focal length, and F/2.8. The"field of view" for each unit is matchied at 2milliradians.

IN'TERFACE DESIGNI

The XI'TR/RCVR interface is packaoed in a doublewidth CAIAC module and fits the standard CAfIAC crate.Figure 2 is a logic diagram of the interface. Linedrivers and receivers are used for the "D" portsignals and also for the "U" ports (TransmitterReceiver Signals) since the laser equipment is lo-cated several hundred feet from, the interface.Power only is obtained from the dataway. Serialhighway signals are passed through the front panel.

The transmitter section consists of a monostable(U13) which sends a pulse whenever the NIRZ (non-return-to-zero) Serial Hlighway data line is logically"zero". This occurs on the hioh-to-loh transitionof the clock pulse. No pulse is transrmitted wheneverthe data line is logically "one".

The receiver section will operate with the standard10 or 11 bits per byte frame. The start bit is alogic "zero" and the stop bit or bits are lonically"one". A local crystal oscillator is dividled downto the frequency of transmission to provide theclock signal. The clock is synchronized by resettinothe decade dividers whenever a start bit is re-ceived. The decade counter (04) and the flip-flop(U7) allow^ a reset pulse only once every ten clockperiods. Flip-flops (U10) are used to recover theNRZ data from the incomlina pulse stream. The firstflip-flop is set to "one" by the clock but is resetto "zero" if a pulse is received from the 736 RCVR.On the rising edge of the clock signal, U0 qeneratesa pulse to transfer data to the second flip-flop.Data is thus delayed one clock period in the receiversection. The interface is desioned to operate atlOkHiz, 50kHiz, 100kHz, and lNI!7z. The logic is imple-nented with TTL integrated circuits rmounted on aprinted circuit board. The line drivers and re-ceivers are SN751 10N and SN75107AN respectively.

PERFOR lANCE

The laboratory facilities are located in an aridregion approximately 800 feet above sea level. Nor-nial weather conditions allow for excellent visibilityexcept for brief fog periods during winter months.Jccasional sandstorms and high winfds are experiencedtvith visibility reduced to a rminimum of .5 km,. Fogconditions have reduced visibility to 200 rietersfor brief periods.

The system, was tested through a computer program)that excercises the system at maxirmumr rate sendingCANAC commands and receiving reply messages. Byinterrogating the SH system status after eacn opera-tion an automatic error analysis of frequency versustime was made.

The error rate wJas shown to be dependent on visibil-ity as presented in Table I. Under any conditionsof visibility in excess of the unidirectional trans-rmission distance thie error rate was less than5 X l0-7, W'ith visibility at twice the transmnitteddistance, the error rate vwas less than 10-10. ,'klldata were accumulated at a transmission rate of1 OkHfz.

TABLE I

Test System Error Rates

Transrmitted Distance: 1.5 kr,

Visibility

.75 km1.5 kri

>1.5 UIs

Bit Error Rate

10-45 x 10-7

<10-10

CUNCLUS I ON

Results indicate that the system w,ill be operational98 percent of thlie tim-ie on a year around basis dueto local weather conditions. Ahs originally sought,the systerm is modular, directly available with minorhardware interfacinn., and is simple to use.

REFEREN4CES

1. CA,-AC. Serial Syster. Organization - A Description,TID-26488, December, 1973.

2. Ibid., Appendix A3, pp 67-76.

3. Amrerican Nlational Standard for thie Safe Use ofLasers, Arierican Nllational Standards Institute,Inc., AINSI-Z136. 1-1973, April 1973.

500

Page 3: A CAMAC Serial Highway Utilizing a Laser Link

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