designimplementa00ande - Calhoun: The NPS
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1. ae _ I A 9049 ae RAN BY WS meee jaa BEER Ja BR _ SSeS ee ARDA Bi EKE EO ps Har E E E en esa Arial 2 he RE PA Seren a E A ead er 4 SS s gt as urges ani pero eas ran ER a A nd E gt 4 7 ee EA ee er et gt 31 e 5 e z 77 t 2 A s t 7 a a 7 lt 4 1 L 5 1 5 4 4 NAVAL POSTGRADUATE SCHOOL Monterey California THESIS DESIGN AND IMPLEMENTATION OF A TOKEN RING FIBER OPTIC LOCAL AREA NETWORK INTERFACE MODULE by Mary L Anderson 44 September 1989 Thesis Advisor John P Powers Approved for public release distribution is unlimited _ 1247162 UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE REPORT DOCUMENTATION PAGE REPORT SECURITY CLASSIFICATION 1b RESTRICTIVE MARKINGS UNCLASSIFIED 2 SECURITY CLASSIFIC2. DISTRIBUTION 15 13 16 16 18 23 228 24 27 29 36 36 36 237 38 I INTRODUCTION A GENERAL During the past few years token passing ring interface techniques have risen as viable technology for local area network LAN applications Simultaneously optical fiber has become the preferred transmission medium for use in long haul communication systems present use of optical fiber within a local area network is limited predominately to networks with a bus topology and utilizing either Carrier Sense Multiple Access with Collision Detection CSMA CD or token passing protocols Ref 1 238 Within token ring LANs present use of fiber optic cable is limited to backbone applications which link individual LANs together while fiber to terminal equipment is rarely implemented Ref 2 74 A use of fiber within token ring LANs will recognized upon final completion of the Fiber Distributed Data Interface FDDI standards These standards describe a fiber optic token ring LAN that operates at 100 Mbps and employs a redundant counter rotating dual ring topology The FDDI standards draw heavily from the existing IEEE 802 5 standard for dual twisted pair copper wire Ref 2 p 78 Reference 3 IEEE 802 5 is the accepted standard for the token passing LAN operating at 4 Mbps and employing a single ring topology The FDD
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4. BACKGROUND 5 AND THE 150 MODEL Local area networks include data computer communication elements that are geographically confined to being less than 10 kilometers apart and generally utilizing a shared transmission media 4 p 6 In relation to the Open System Interconnection ISO model local area network standards and protocols are applied at the lowest two layers as depicted in Figure 1 The lowest layer the physical layer defines the actual electrical and mechanical connections The next layer the Data Link layer Flgure 1 ISO Reference Model LOGICAL LINK CONTROL LLC MEDIUM ACCESS CONTROL MAC is divided into the Medium Access Control and Logical Link Control LLC sublayers Together these sublayers define the way that data is formatted for transmission and how access to the network is controlled Ref 5 p 1 3 There are several different MAC sublayers depending on the LAN topology and protocol Some examples of MAC technology include star wired ring topology using token passing access bus topology using CSMA CD access and o bus topology using token passing access B TOKEN RING PROTOCOL Although this research is confined predominately to the physical layer a reasonable understanding of the MAC technology of the star wired ring topology using token passing protocol is considered essential Figure 2 illustrates the token access control mechanism
5. 1 lt fon s pr uE 6 H 9 0 Figure 8 22 DESIGN DESCRIPTION AND EVALUATION A DESIGN APPROACH With the required signal completely characterized the choice of using analog or digital techniques to implement the design had to be made The final design was decided by the available circuit components The fiber optic receiver selection was the primary factor in the decision to employ analog methods One available digital fiber optic receiver HFBR 2402 by Hewlett Packard is capable of supporting data rates up to 5 MBaud Ref 8 p 4 31 The LAN data rate of 4 Mbps using differential Manchester coding required 8 Mbaud of coded data however This exceeded the capabilities of the HFBR 2402 so we required the use of a different receiver An available analog fiber optic receiver HFBR 2404 by Hewlett Packard was capable of supporting data rates up to 50 Mbaud with the appropriate output circuitry and more than adequately met the data rate requirement Ref 8 p 4 33 This resulted in the decision to use analog data transmission in the fiber optic link The HFBR 2404 receiver has a maximum receive signal pin voltage of 1 volt This produced the requirement to amplify the electrical output from the optical receiver to the signal voltage of 3 0 4 5 volts peak to peak that the LAN requires The selection of an operational amplifier to preform this 23 amplification w
6. Figure 12 Oscilloscope Display of Received Signal at 2 MHz and 4 2 volts peak to peak Figure 13 Oscilloscope Display of Received Signal at 4 MHz and 3 8 volts peak to peak 31 Figure 14 Figure 15 Oscilloscope Display of Received Signal at 7 MHz and 3 8 volts peak to peak Oscilloscope Display of Received Signal at 4 MHz Showing a 24 30 ns Transit Time Between the 10 and 90 Voltage Levels as marked by the cursors 32 further evaluate the design a duplicate fiber optic link was constructed for experimental insertion into the LAN Referring to Figure 16 the input signals to the fiber optic links are the LAN signals from the wiring concentrator the output signals are fed to the receive pair on the LAN adapter card Figure 17 shows the input LAN signal to the fiber optic link Figure 18 shows the corresponding LAN signal at the distant end of the fiber optic link after successful transmission through the link Com puter Computer vu Wiring t RCV 0 Config ured Configured U 2 1 Concentrator IRCV2 1 as USER as SERVER Fiber Optic Link Figure 16 Local Area Network System Block Diagram with Inserted Fiber Optic Link 33 YA AA f A Maree Figure 17 Oscilloscope Display of LAN Signal of the Input to the Transmitter circuit 4 volts peak to peak Figure 18 Oscilloscope Display of LAN Signal at the Output of the Re
7. 11 capacitor values microfarads Figure 10 Receiver Circuit Schematic 28 2 RECEIVER CIRCUIT COMPONENT VALUES OPTICAL D DESIGN EVALUATION The design evaluation started with the requirement to pass the modeled LAN signal over the fiber optic link and correctly recover the signal at the distant end LAN signal was modeled as a square wave with frequencies varying from 1 to 4 MHz using a signal generator These signals were applied to the optical transmitter circuit of Figure 9 and measured at the output of the receiver circuit of Figure 10 The varying frequencies account for the dissimilar number of level transitions between a series of data zeros a series of data ones and the non data J K sequence The received signals at 1 MHz 2 MHz 4 MHz and 7 MHz are shown in Figures 11 though 14 respectively The ripples seen in the 2 MHz and 4 MHz signals of Figures 12 and 13 respectively were produced at the transmitter by the signal generator Note that in Figure 14 the 7 MHz received signal no longer resembles the input square wave and so provides an 29 upper signal rate bound Referring to Figure 15 the design criteria of a transit time of less than 25 ns between the 10 and 90 voltage levels is depicted This demonstrates the modeled received signal meets the transit time design criteria Figure 11 Oscilloscope Display of Received Signal at 1 MHz 3 8 volts and peak to peak 30
8. A token is an access granting unique symbol sequence that circulates from station to station on the ring In our system the token is 3 bytes in length and consists of a starting delimiter field SDEL an access control field AC and an ending delimiter field EDEL Each of these fields is 1 byte in length The SDEL symbol sequence is JKOJKOOO This pattern is used by the adapter for synchronization The J and K symbols are deliberate Manchester code violations that do not have mid bit transition Manchester coding and these symbols are discussed more detail Chapter field byte contains the token indicator bit 6 bits for priority indication and reservation and the monitor count bit token indicator bit differentiates between a free token and a frame The priority indication and reservation bits provides the mechanism within the token ring protocol for prioritizing access on the ring priority levels are limited to 0 through 3 as are the reservation levels The monitor count bit is used by the Active Monitor An Active Monitor is the station on the ring that has the responsibility for ensuring normal ring operation Active Monitor receiving 1 the monitor count bit indicates a frame or reserved token was not properly removed from the ring Active Monitor then purges the ring and generates a free token The EDEL symbol sequence is JK1JK10X Bit 7 of this sequence is a
9. Circulating token station transmit upon receiving the token b Station A seizes token transmits frame of data addressed to station C Figure 2 Token Access Control for Message 10 Station receives frame address and repeats frame 4 Station C receives frame recognizes address acknowledges receipt and repeats data Figure 2 cont 11 Station D repeats frame f Station receives acknowledgement and repeated data transmits free token only the cycle repeats Figure 2 cont 12 TMS380 LAN ADAPTER CHIPSET Texas Instruments and IBM jointly developed the integrated architecture of TMS380 chipset for connecting equipment to a token ring LAN Figure 3 is a block diagram of the TMS380 chipset consisting of five integrated circuit devices The TMS38030 system interface SIF chip provides the means to transfer data between the LAN adapter environment and the host system The SIF asynchronously connects the host system bus operating at data rates up to 5 Mbytes sec to the LAN adapter bus operating at 6 Mbytes sec The SIF provides both direct memory access DMA and direct I O DIO transfers between these buses A 16 bit high performance CPU with on chip buffer RAM is contained on the 538010 communications processor The dedicated CPU and RAM were designed to minimize the LAN adapter overhead burden on the host system by handling all the non real t
10. for this impedance matching resistor was not apparent When the final fiber link was inserted into the LAN however the value of this resistor determined whether or not the LAN functioned properly When this resistor is too small an adapter hardware error message from the Token Ring connection Adapter program is received and access to the network is denied However when this resistor is too large access to the network menu is granted but communications between the two computers is not achieved Although the exact cause of this inability to communicate is not known it is theorized that the impedance mismatch interferes with the ring polling process This process enables the computer to acquire the specific address of its upstream neighbor Since these computers are the upstream neighbors of each other without an upstream neighbor address they do not recognize each other as network stations and therefore cannot communicate HFBR1 402 R2 01 R EL2020C INPUT SIGNA LIGHT 1097 NOTE 1 All op amp power supplies are capacitively coupled to ground by 4 7uF tantalum capacitors NOTE 2 All capacitor values are in microfarads Figure 9 Transmitter Circuit Schematic 26 TABLE 1 OPTICAL TRANSMITTER CIRCUIT COMPONENT VALUES C THE RECEIVER CIRCUIT DESIGN The receiver design Figure 10 accepts the incoming modulated light signal converts it to an electrical signal and amplifies the electrical signal throu
11. of R1 experimentally determined As the value of 1 increases the current through the transmitter LED decreases thereby reducing the optical output power If this resistor is too large it causes the transmitter LED to operate near cut off resulting in a distorted output signal However if this resistor is too small it causes the optical receiver to saturate resulting in a clipped signal The required value of 1 was experimentally determined to be 150 This value resulted in an undistorted signal being obtained by the optical receiver The transmitter circuit performs the two basic functions of providing a biased signal to the optical transmitter and providing impedance matching to the signal source The voltage divider network of R4 and 5 is used to supply pre bias drive current to the optical transmitter to obtain a faster response time from the LED The EL2020C is used in the inverting mode as a voltage summer One input of the summer is the 3 volts supplied by the voltage divider while the other input is the LAN signal of approximately 2 volts i e 4 volts peak to peak The output of the summer is the biased signal used to directly intensity modulate the optical transmitter impedance matching to the LAN signal source is provided by R8 The value of R8 was experimentally determined to be 2KN During the initial testing of this design using 25 signal generator to produce the model of the LAN signal the need
12. protocol for frame format information and token boundary synchronization Ref 5 p 3 6 This is accomplished by the detection and exploitation of missing mid bit transition within the non data J and K symbols Figure 7 taken at point B of Figure 8 is the signal to be modeled showing the data and non data symbols The wider sequence in the right center of Figure 7 depicts the non data J and K symbols surrounding narrower sequence in Figure 7 depicts the binary one and binary zero symbols 20 data signaling rate is 4 Mbps Referring to Figure 8 at points B or 0 the transmitted signal is required to be between 3 0 4 5 volts peak to peak The voltage changes between the 10 and 90 points of the output signal cannot exceed 25 ns Ref 3 p 80 signal of Figure 7 conformed to these requirements and was measured at 4 4 volts peak to peak with transitions between the 10 and 90 voltage levels occurring in 22 ns IN Figure 7 Oscilloscope Display of the Signal to be Modeled 4 4 volts peak to peak 21 515 Je EIVND3 dVOOUN ODYINI v vnDd3 8NIADU amp 99 BASH BABO vinowd WLx LSOBESWL 38X907 1MON190 NIX901 84205 VdDODA HILT NVIDIA 3I8vN3 17198 LUSN 123M ZSOBESWL Output Interface Circuit
13. ATION AUTHORITY 3 DISTRIBUTION AVAILABILITY OF REPORT Approved for public release distribution is unlimited 26 DECLASSIFICATION DOWNGRADING SCHEDULE 4 PERFORMING ORGANIZATION REPORT NUMBER S 5 MONITORING ORGANIZATION REPORT NUMBER S 6a NAME OF PERFORMING ORGANIZATION 6b OFEEEBUMBOL 7 NAME OF MONITORING ORGANIZATION If applicable Naval Postgraduate School Naval Postgraduate School 62 ADDRESS State and ZIP Code 7b ADDRESS City State and ZIP Code Monterey California 93943 5000 Monterey California 93943 5000 NAME OF FUNDING SPONSORING 85 OFFICE SYMBOL 9 PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER ORGANIZATION If applicable 8 ADDRESS City State and Code 10 SOURCE OF FUNDING NUMBERS PROGRAM PROJECT TASK WORK UNIT ELEMENT NO NO NO ACCESSION NO 11 TITLE Include Security Classification DESIGN AND IMPLEMENTATION OF TOKEN RING FIBER OPTIC LOCAL AREA NETWORK INTERFACE MODULE 12 PERSONAL AUTHOR S ANDER SO 13 136 TIME COVERED 14 DATE OF REPORT Year Month Day 15 PAGE COUNT Master s Thesis FROM TO 1989 September 43 16 SUPPLEMENTARY NOTATI ON The views expressed in this thesis are those of the author and do not reflect the official policy or position of the Depart ment of Defense or the U S Government 17 COSATI CODES 18 SUBJECT TERMS Continue on reverse if necessary and identify by block number Token Ring fiber opt
14. I standards deviate from the IEEE 802 5 standard only when required its higher data rate and the intrinsic differences between electrical and optical signals THESIS OBJECTIVES The subject of this thesis is a hardware design of a fiber optic LAN interface module The initial objective was to identify and model the electrical signal produced by the token ring LAN The next objective was to design and build a fiber optic link and then to pass the modeled signal over the link and correctly recover the signal at the distant end The final objective was to transparently insert the fiber optic link into the LAN A transparent insertion is being defined here as conforming to the following criteria meet existing standards of Reference 3 developed for dual twisted pair copper wire o not adversely affect the software protocol and o allow the LAN to communicate over the fiber optic link C THESIS ORGANIZATION Chapter II provides the necessary background to ensure a baseline knowledge of local area networks with special emphasis on token ring access and implementation Chapter III presents design specifications and thoroughly describes the existing network system components Chapter IV deals with detailed design construction and operation of the hardware that was built In addition Chapter IV also presents the design performance when implemented within the LAN followed conclusions and recommendations in Chapter
15. allation of the other LAN programs The Token Ring Connection Adapter program provides the LAN adapter software interface This program package tests the LAN adapter board to insure that it is functioning properly and then enables the computer with an installed LAN adapter board to operate as part of a network The NETBIOS Network Basic Input Output System is a network software interface that runs on top of the adapter software interface to link LAN adapter software to the host computer PC Token Ring LAN is menu driven application program that runs on top of NETBIOS This application program allows network users the ability to perform variety of computer activities including sending and receiving messages using network disks and directories utilizing network printers and displaying the network status Installation and use of these programs are thoroughly explained in References 6 and 7 DESCRIPTION OF SIGNAL BE MODELED Interconnection of data processing equipment by way of a local area network configured in star wired ring topology and 18 using token passing access method described by Reference 3 the ANSI IEEE 802 5 standard This standard provided the baseline for the signal to be modeled The signal consists of the following four differential Manchester encoded symbols 0 binary zero 1 binary one J non data J non data K Differential Manchester coding is characterized by two symbol element
16. as based the need for fast settling time and a wide bandwidth As mentioned earlier the LAN signal is required to transit between the 10 and 90 voltage levels in less than 25 ns this was the driving specification in the op amp finally chosen The EL2020C by Elantec has 1 settling time of 50 ns but transits between the 10 and 90 voltage levels typically within 25 ns Ref 9 pp 80 82 B THE TRANSMITTER CIRCUIT DESIGN The transmitter design is built around a direct intensity modulation scheme In this scheme the transmitted signal is used to directly modulate the light source intensity To accomplish this a DC bias voltage is applied to the LAN Signal converting it from a bipolar signal having both positive and negative polarities to a unipolar signal having only a positive polarity This conversion is required due to the unipolar nature of light i e light can have varying intensities but only a single polarity The response time of the light source and the time constant of the circuit that provides the drive current determine the maximum rate for direct intensity modulation The complete transmitter circuit design is shown in Figure 9 with component values given in Table 1 The optical transmitter utilized was the HFBR 1402 by Hewlett Packard This transmitter is an LED device utilized for both analog and digital designs The wiring of the HFBR 1402 Figure 9 24 is directly from Reference 8 with the exact value
17. ceiver Circuit 4 2 volts peak to peak 34 final evaluation of the design was question of transparency A transparent insertion as defined in Chapter I conforms to the following criteria o meet existing standards of Reference 3 developed for dual twisted pair copper wire o not adversely affect the software protocol and allow the LAN to communicate over the fiber optic link Using the NCR network software messages were passed from one computer to the other over the design link and were accurately received NCR network software allows the direct use of a network computer s hard disk drive by another computer the network This feature was also used to evaluate the design link Using the LAN computer without the fiber optic link the User flle was created and saved on hard drive of the LAN computer with the fiber optic link the Server This same file was then repeatedly recalled by the user computer modified and saved back on the server computer s hard drive with complete accuracy Although not exhaustive the evaluation of this design supplies documentation of all original objectives as stated in Chapter 1 35 CONCLUSIONS AND RECOMMENDATIONS CONCLUSIONS This thesis accomplished the design goal of producing fiber optic link for a token ring LAN ultimate test of this link would be to utilize it in both the transmit and receive signal pairs This is not possible due to the AC nature
18. ed These cards are commercially available from NCR Corporation 16 wiring concentrator is a series of electrical switches which function to serially insert individual stations into the ring The wiring concentrator is a passive device which is powered by the phantom drive of the ring interface which impresses a DC voltage on the transmit pair to cause the switching action Figure 5 exemplifies the device insertion and bypass action of the wiring concentrator WIRING CONCENTRATOR 1 zn ES ATTACHING ATTACHING ATTACHING PRODUCT PRODUCT PRODUCT E INSERTED DE INSERTED INTO RING FROM RING Figure 5 Token Ring Wiring Concentrator from Ref 5 p 1 4 The LAN cables are terminated at one end with a male 9 pin subminiature D connector and terminated at the other end with a Medium Interface Connector The D connector attaches to the installed LAN adapter card and the MIC attaches to the wiring concentrator The existing network software includes NCR Corporation versions of PC Token Ring System Installation Token Ring 17 Connection Adapter NETBIOS and Token Ring LAN When installed these four program packages provide all the necessary software except DOS for the operation of a token ring LAN The PC Token ring System Installation program is a menu driven software package that prompts the user through the correct inst
19. epicts station A after taking possession of the token transmitting a data frame Each station when it is not the possessor of the token functions as a repeater A receiving station reads the frame and determines its destination If the frame destination is not the received station the station repeats retransmits the frame This repeater function is depicted in Figure 2c Figure 24 depicts station as the frame s intended destination The destination station copies the data and acknowledges receipt This acknowledgement is accomplished by setting the frame copied FC indicator bits in the frame status field to 1 The destination station is also required to retransmit the frame Once the data is received and acknowledged it is the responsibility of the frame source station to remove its data from the ring and generate a new token Figure 2e shows station A completing the transmission of the frame Figure 2f depicts the originating station A removing its data from the ring and generating the new token Ref 5 pp 1 5 to 3 16 Since all stations wait for the token to transmit data and the station possessing the token has exclusive use of the transmission media collisions two stations attempting to transmit simultaneously do not occur This protocol therefore produces a reliable deterministic approach to LAN communications and eliminates the performance uncertainties of collision based LAN protocols
20. evel This ensures interoperability and LAN connectivity within a token ring network In summary this chapter supplied a baseline knowledge of token ring LANs This baseline included a review of the ISO model as it related to token ring LANs a discussion of the token ring protocol and a description of the TMS380 chipset Chapter III presents the design requirements using these baseline concepts 14 YIOMLIN gt 25085511 32 34831 _ ONIH U3IONVYH 10I0104d OZOBESWL LSO8ESWL WILSAS O O8ESWL 5 8 4 NVI 055320 4 SNOILVIINAWWOI 010865011 LASdIHD H3ldVOV NVI O8ESWL 1 7 5 5380 Adapter Chipset Block Diagram from Ref Figure 3 15 DESIGN REQUIREMENTS A MICROCOMPUTER SYSTEM CONFIGURATION Figure 4 is a block diagram showing the microcomputer system that provided the basic token ring LAN configuration for this thesis This system consisted of o two IBM XT clones wiring concentrator also referred to as a wiring hub multiple access unit MAU or trunk coupling unit and two PC token ring adapter cables Computer XMT 1 Computer 1 1 2 7 Configured as USER as SERVER Token Ring Z Adapter Cable Figure 4 Local Area Network System Block Diagram Each of the IBM XT clones had a token ring LAN adapter card based on the TMS380 chipset install
21. gh a series of stages to recreate the LAN signal The complete receiver circuit design is shown in Figure 10 with component values given in Table 2 stated previously the optical receiver utilized was the HFBR 2404 by Hewlett Packard This receiver contains a PIN photo diode and Produces an inverted analog voltage replica of the received optical signal Although the actual internal wiring of the HFBR 2404 is not explicitly supplied in Reference 8 connecting the device is straightforward The amplification stages of the receiver were mathematically determined and experimentally optimized The gain was accomplished in stages to maintain a wide bandwidth Not doing so would result in severe signal distortion For a given gain the bandwidth can be increased by decreasing the feedback resistor but reducing the feedback resistor results 27 excessive overshoot ringing and eventually oscillations Four stages were experimentally determined to balance this gain bandwidth tradeoff gain of each stage listed in order from the detector are inverting gain of 2 inverting gain of 10 inverting gain of 1 5 and inverting gain of 1 The last stage corrects the polarity of the output signal to match the original signal from the transmitter 92 EL2e2ec U3 EL2020C 04 EL202ec OUTPUT SIGNAL NOTE 1 11 op amp power supplies are capacitively coupled to ground by 4 7uF tantalum capacitors NOTE 2
22. ic local area network 19 ABSTRACT Continue on reverse if necessary and identify by block number This thesis describes the design and implementation of a token ring fiber optic local area network LAN interface module The token ring protocol implementing the IEEE 802 5 standard is reviewed The initial LAN electrical signal operating at 4 Mbps is provided by a LAN adapter card based on the TMS380 chipset developed for twisted pair copper wire This design features analog implementations of both the input electrical circuitry of the optical transmitter and output electrical circuitry of the optical receiver Successful LAN communications over the fiber optic link are described 20 DISTRIBUTION AVAILABILITY ABSTRACT UNCLASSIFIED UNLIMITED 0 SAME AS RPT O otic users UNCLASSIFIED 22a NAME OF RESPONSIBLE INDIVIDUAL 22b TELEPHONE include Area Code Form 1473 JUN 86 Previous editions are obsolete SECURITY CLASSIFICATION OF THIS PAGE _ S N 0102 LF 014 6603 UNCLASSIFIED 1 Approved for public release distribution is unlimited DESIGN AND IMPLEMENTATION TOKEN RING FIBER OPTIC LOCAL AREA NETWORK INTERFACE MODULE by Mary L Anderson Lieutenant United States Navy B A Central University of Iowa 1978 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING from the NAVAL POSTGRADUATE SCHOOL September 1989 ABSTRACT This the
23. ime LAN functions These functions include controlling the operations of the SIF preforming adapter bring up diagnostics executing the MAC protocol managing the frame buffers with the on chip RAM and maintaining a working storage space also with the on chip RAM The TMS38020 protocol handler performs the real time hardware based protocol functions compatible with the IEEE 802 5 standard These functions include differential Manchester encoding and decoding of data recognizing frame addresses and capturing free tokens The protocol handler 13 also contains of 16 bytes of software used the communication processor Jointly the two chips TMS38051 and TMS38052 are the ring interface Collectively they connect the station to the LAN through separate transmit and receive channel pairs In addition they provide the phantom drive signal to physically insert the station into the ring The phantom drive impresses a DC voltage on the transmit pair This DC voltage is transparent to the station s transmitted data hence the name phantom The impressed DC voltage is used by the wiring concentrator to control relays that insert the station serially into the ring Loss or absence of the phantom drive voltage results in the station being bypassed or removed from the ring Ref 5 p 1 8 Use of a token ring LAN adapter card based on this chipset eliminates incompatibilities that could arise even at the chip l
24. l Dayton Ohio 1987 Hewlett Packard Company Opto Electronics Designer Catalog Palo Alto CA 1986 Elantec Inc Elantec High Performance Analog Integrated Circuits Data Book Milpitas CA 1988 37 INITIAL DISTRIBUTION Library Code 1424 Naval Postgraduate School Monterey California 93943 5000 Chairman Code 62 Department of Electrical and Computer Engineering Naval Postgraduate School Monterey California 93943 5000 Prof John P Powers Code 62Po Department of Electrical and Computer Engineering Naval Postgraduate School Monterey California 93943 5002 Curricular Officer Code 32 Naval Postgraduate School Monterey California 93943 5000 Prof Tri T Ha Code 62Ha Naval Postgraduate School Monterey California 93943 5000 Defense Communication Agency ATTN LT M L Anderson Code B 541 Washington DC 20305 2000 Commander Space and Naval Warfare Command ATTN Mr M Potosky PDW 180 Washington DC 20370 5000 Defense Technical Information Center Cameron Station Alexandria Virginia 22304 6145 38 No Copies Thesis 4585 Anderson Design and implementa tion of a token ring fiber optic local area network interface module 37 aut Design implementation of token rin III 3 2768 000 88125 4 DUDLEY LIBRARY o ee 5 0
25. me MAC control frames execute the MAC layer protocol as discussed in Reference 3 This protocol implements a comprehensive set of problem determination resolution and reporting functions Through the MAC frames the ring communication problems are rapidly diagnosed and corrected MAC frames originate from and processed the station adapters Therefore the operation of MAC protocol is completely transparent to the individual host computers and provides a functionally reliable LAN Source and destination address fields are each 6 bytes in length These fields identify the frame s originator and the frame s intended receiver The information field contains the data to be transmitted The maximum length of this field is 4027 bytes The Frame Check sequence field contains a 32 bit cyclic redundancy code CRC that is used to protect the FC DA SA and information fields he frame s source station provides the CRC that is used in the FSC field when the frame is transmitted Each adapter calculates the CRC by a polynomial that is serially accumulated as the frame is transmitted or received received in the FSC field is compared to the adapter s calculated value to verify that the frame was received without error The frame status field is 1 byte in length This field indicates to the frame source whether the frame destination address was recognized and if the frame was copied by the destination station Figure 2b d
26. n error detected indicator This bit is 0 for no error and 1 for error detected EDEL like the SDEL 15 used by the adapter for synchronization The possessor of the token has exclusive use of the transmission media single token circulates on the ring thereby giving each station on the net an opportunity to transmit data when it receives the token Figure 2a depicts a free token circulating the ring When a station has data to transmit it captures the token and changes the token status to busy This is accomplished by changing the token indicator bit the AC field of the token from 0 to 1 the token indicator bit signifies frame vice free token station then transmits data frame The data frame format is strictly defined by the token ring protocol and consists of the following fields listed in order of ring transmission o Starting Delimiter field SDEL o Access Control field AC o Frame Control field FC o Destination Address DA o Source Address SA o Information field data Frame Check Sequence field FCS o Ending Delimiter EDEL and Frame Status field FS The bit sequence of the SDEL AC and EDEL fields ina data frame is identical to the respective fields of a token with the exception of the set token indicator bit as previously discussed The FC field is 1 byte in length and indicates the frame type as a MAC control frame or non MAC control fra
27. of the optical receiver circuit and its inability to pass the DC voltage provided by the phantom drive Recall that phantom drive activates the relays of the wiring concentrator to insert the station into the ring Within fiber optic LAN the insertion is accomplished by control information carried by special MAC frames Ref l p 240 B RECOMMENDATIONS The following list provides follow on research topics in this area and includes both hardware and software issues Modify write the software to allow insertion into the ring via MAC frames Replace the wiring concentrator with optical fiber star coupler Multiplex the transmit pair and receive pair to reduce the cable requirement from 4 to 2 optical fibers 36 REFERENCES Werner Token Ring Local Area Networks Their Performance Proceedings of the IEEE Vol 77 No 2 238 255 1989 Greenfield David Chasing the Light Fiber Optic LANS for Today and Tomorrow LAN Magazine pp 63 78 August 1989 ANSI IEEE Standard 802 5 Token Ring Access Method and Physical Layer Specifications IEEE Incorporated 1985 Keiser Gerd E Local Area Networks McGraw Hill Inc 1989 Texas Instruments Incorporated 5380 Adapter Chipset User s Guide 1985 NCR Corporation NCR PC Token Ring System NCR PC LAN Program User s Manual Dayton Ohio 1987 NCR Corporation NCR PC Token Ring System NCR PC LAN Program Administration Manua
28. s per bit with a forced mid bit transition Figure 6 pictorially describes the differential Manchester coding used within a token ring LAN BINARY BINARY BINARY BINARY BINARY NON NON ONE ZERO ONE ONE ZERO DATA J DATA K 1 ns ude TEK NONE BINARY CODE NRZ DIFFERENTIAL MANCHESTER CODE Figure 6 Example of Symbol Encoding from Ref 3 p 74 19 polarities of the line signal element sequence depends on the polarity of the trailing symbol element of the previously transmitted data or non data bit If a binary zero is to be transmitted the leading symbol element is opposite of the trailing symbol element of the previous bit and there is a forced mid bit transition If a binary one is to be transmitted the leading symbol element is the same as the trailing symbol element of the previous bit and there is also forced mid bit transition non data symbol J has the same polarity as the trailing symbol element and there is no mid bit transition non data symbol K has the opposite polarity as the trailing symbol element and again there is no mid bit transition Ref 3 p 73 The use of this encoding process transforms one bit into two baud two symbol elements per bit A two baud structure allows the coding of the four symbols binary one binary zero non data J and non data K The non data J and K symbols are used within the token ring
29. sis describes the design and implementation of a token ring fiber optic local area network LAN interface module The token ring protocol implementing the IEEE 802 5 standard is reviewed The initial LAN electrical signal operating at 4 Mbps is provided by a LAN adapter card based on the TMS380 chipset developed for twisted pair copper wire This design features analog implementations of both the input electrical circuitry of the optical transmitter and output electrical circuitry of the optical receiver Successful LAN communications over the fiber optic link are described 111 TABLE CONTENTS I INTRODUCTION 2 GENERAL O ee B THESIS OBIE CTI VES THESIS 151 BACKGROUND RS a aa a ee LANS AND THE ISO MODEL TOKEN RING TMS380 LAN ADAPTER III DESIGN REQUIREMENTS ere era MICROCOMPUTER SYSTEM CONFIGURATION B DESCRIPTION OF SIGNAL TO BE MODELED DESIGN DESCRIPTION AND DESIGN THE TRANSMITTER CIRCUIT DESIGN C THE RECEIVER CIRCUIT DESIGN DESIGN CONCLUSIONS AND RECOMMENDATIONS 5 5 5 REFERENCES
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