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1. TEP TECHNICA CO LTD TEP O TECHNICA CUnet Technical Guide For Network Note 1 The information in this document is subject to change without prior notice Before using this product please confirm that this is the latest version of this document 2 Technical information in this document such as explanations and circuit examples are refer ences for this product When actually using this product always fully evaluate the entire sys tem according to the design purpose based on considerations of peripheral circuits and the PC board environment We assume no responsibility for any incompatibility between this product and your system 3 We assume no responsibility whatsoever for any losses or damages arising from the use of the information products and circuits in this document or for infringement of patents and any other rights of a third party 4 When using this product and the information and circuits in this document we do not guaran tee the right to use any property rights intellectual property rights and any other rights of a third party 5 This product is not designed for use in critical applications such as life support systems Con tact us when considering such applications 6 No part of this document may be copied or reproduced in any form or by any means without prior written permission from StepTechnica Co Ltd TEP STECHNICA CO LTD Technical Guide2. resistors may be placed both before and after signals pass through the pulse transformer so that the relationship between the pulse transformer and the termination resistor can be identified Fig 9 2 N 100 Q termination resistor Network cable with impedance of 100 0 Place before or after pulse transformer Signalsource bere ee Receiver in final position e oQ oQ Signals pass as if not through CXX XXD pulse transformer The higher inputimpedance ofthe receiver provides an electric wire to which nothing is connected Fig 9 2 Signal Transparency efolente The pulse transformer need not be used for user systems that do not require the advantages aa i described in item 9 1 Advantages of Pulse Transformer The CUnet ICs operate correctly regardless of whether a pulse transformer is used or not aa A ya TECHNICA Co LTD CUnet 10 Hot swap The user system may require hot swapping of the equipment with CUnet In this case some preventive measures must be taken to prevent disconnecting the multi drop connected lines in the middle of the net work For example Figure 10 1 and 10 2 show connection using two modular connectors E When this connectoris pulled the equipmentto the rightis separated fromthe equipmenttothe left To A Se To other equipment Keep wiring on the circuit board as shortas possible Keep electric wiring from driver receiver components to pins s
3. eeaeee vohcnetdenutiuete 11 Fig 6 Structure of Twisted Pairs and Handling Unused Twisted Pairs 12 Fig 7 Shielded Network Cable 13 Fig 8 How to Test Sensitivity and Regenerative Ability of Receiver 15 FIG Gel PUSO TranSlOmme nti Leelee es Se ads 16 Figs 9 2 Signal TANS Paremey nease te neee en e e e EE EEEE Eai E Eiaa eaae 17 Fig 10 1 Connection between Equipments Using Two Modular Connectors 18 Fig 10 2 Hot swap of Individual Equipments Using Sub circuit board 18 Fig 11 Noise Test in Half duplex Mode 19 TEP STECHNICA CO LTD Technical Guide for Network 1 Recommended Network A CUnet is a system that operates in half duplex communication mode When using the CUnet the network connections shown in Figure are recommended TRX driver receiver in the figure consists of pulse transformer and an RS 485 differential driver and receiver This TRX provides electrical isolation between the CUnet dedicated ICs CUnet ICs and the network cable s Recommended network cables include Ethernet LAN network cables 10BASE T Category 3 or higher and shielded network cables 7 Equivalent to ADM1485 i CUnet IC LSI driven at 5 0 V Network cable dice ee gt HDi l O J Pulse transformer Atwisted pair cable with impedance of 100Q TRX G 2 Multi drop Network In the CUnet network cables between CUnet ICs can be connecte
4. normal clock of less than 500 m Vp p a square wave and a sine wave signal with a duty ratio of 50 After these clocks are input observe whether the differential receiver output a logic signal a square wave with a duty ratio of 50 giving a slight duty collapse of less than 5 fe N Observation of inputwaveform Eithersquare wave or sine wave signal available Signal with duty ratio of 50 Function generator etc 200 mVp p Jai O 000 Observation of output waveform E _ Receiver to be tested naa N Duty ratio of 50 Clock component p suchas crystal co H LM oscillator Waveform observation with oscilloscope Regulate input signal Non conforming receivers shows visible duty collapse by variable resistor o J Fig 8 Howto Test Sensitivity and Regenerative Ability of Receiver 15 EP T STECHNICA CO LTD CUnet 9 Using Pulse Transformer A pulse transformer should be used in the CUnet network This section describes the advantages in using a pulse transformer and the transparency of signals 9 1 Advantages of Pulse Transformer Using a pulse transformer in the CUnet offers the following three advantages 1 Electronic components such as circuit boards containing CUnet ICs can be electri The winding ratio of the i pulse transformer mustbe 1 1 cally insulated from the network Fig 9 1 GG 2 If there is no pulse transformer and a
5. LTD 5 Prohibition of Stub Connection Leader When using network cables in the CUnet network do not make any multipoint connection between the cables with a stub leader Fig 5 2 The reason is explained below The electrical characteristics are different between the connection without a stub Fig 5 1 and the multi point connection with a stub Fig 5 2 The connection without a stub Fig 5 1 can match impedance whereas the multipoint connection with a stub Fig 5 2 causes impedance mismatching at the stub branch Like ripples spreading across water the multipoint connection with a stub Fig 5 2 causes signal reflection and loss of propagation energy Therefore the multipoint connection with a stub Fig 5 2 is not suitable for the network using CUnet network cables Connection oftwo cables Signal source energy source aj Waves spreading from side to side Fig 5 1 Connection without Stub Impedance mismatch occurs here a 1000 100 Waves are reflected Impedance mismatching Stub Leader Signalsource Wave energy is limited Fig 5 2 Connection with Stub 11 EP T STECHNICA CO LTD CUnet 6 Handling Unused Twisted Pairs In the network cable composed of multiple twisted pairs each twisted pair has different twisting pitches Fig 6 which prevents interference crosstalk between signals propagated between twisted pairs When using a ne
6. Recommended Network ein 7 2 gt Multizdrop NetWOrK oere A ia 7 3 Principle of Terminating Network CableS 8 3 1 Signal Propagation Analogy ei lides 8 3 2 Actual Electric Signal Propagation nono 9 4 How to Connect Termination Resistor nono 10 5 Prohibition of Stub Connection Leader i 11 6 Handling Unused Twisted Pairs andanada nncccncninenennns 12 7 Selecting Network Cable cocinada ie Rai 13 8 Howto Select Differential Driver Receiver Component 14 8 1 Selecting Differential DIV 000 ia 14 8 2 Selecting Differential Receiver rre iii 14 9 Using Pulse Transito Merino 16 9 1 Advantages of Pulse Transformer iii 16 9 2 Signal Transparency When Using Pulse Transformer 17 TOMO ES WAPA a 18 11 How to Conduct Tests and Results e 19 TEP STECHNICA Co LTD CUnet Figures Fig 1 Connection in Half duplex Mode 7 Fig 2 Multi drop Network in Half duplex Mode 7 Fig 3 1 Propagation of Waves 322 iii biella boe 8 Fig 3 2 Actual Electric Signal Propagation 9 Fig 4 Termination in Half duplex Mode 10 Fig 9 1 Gonnection without StUb secc o Eee le iene ei 11 AE Bo SAA cre tests euntden
7. a severe test StepTechnica carried out more than 48 hours of continuous operation tests on the CUnet at each baud rate by injecting noise 40 times per second for 48 hours and con firmed that neither garbage data nor malfunctions occurs in the CUnet AIN For details of noise tests refer to 6 Data Quality Assurance in CUnet Introduction Reference RO RI Guide 4 S Noise generating simulator circuit Oto2us atrandom Generates pulses more than 40 times per second at random CUnet IC Pulse transformer Pulse 9 transformer Connect62 pcs CUnet IC CUnet IC Fig 11 Noise Testin Half duplex Mode 19 E North America Distributor Trans Data Technologies Inc 340 Arthur Ave Roselle IL 60172 Telephone 630 440 4075 Facsimile 630 539 4475 e mail info steptechnica us http www steptechnica us E Developed and manufactured by Step Technica Co Ltd 757 3 Shimo fujisawa Iruma shi Saitama 358 0011 TEL 04 2964 8804 FAX 04 2964 7653 http www steptechnica com info steptechnica com CUnet Technical Guide for Network Document No STD CUTGN V1 1E Issued June 2008
8. d on multi drop network Figure 2 shows the multi drop network in half duplex mode The user must connect a termination resistor to the end both ends of these multi drop connected network cables to match impedance Equipment with CUnet 100 Q network cable used Equipmentwith CUnet Driver Receiver Driver Receiver CUnetIC CUnetIC Fig 2 Multi drop Network in Half duplex Mode EP T STECHNICA CO LTD CUnet 3 Principle of Terminating Network Cables When using a network cable to build a CUnet network the user must connect a termination resistor with the same impedance value as that of the network cable to both ends of the network cable The purpose of connecting termination resistor is to allow signals to be transmitted to the receiving system without interference such as waveform breakedown and waveform disappearance The principle is shown below 3 1 Signal Propagation Analogy Figure 3 1 illustrates signal propagation using the analogy of ripples spreading across water 1 The propagation of digital signals is compared to ripples spreading across water 2 When the waves hit obstacles they are reflected to return 3 If the waves do not hit an obstacle they never return Ripples spread across water Waves are reflected by the walls Waveforms on water EE have clear sine curves Reflected gt did 4 waves I Can be higher than e oi signal source Overlapped wave
9. d to an infinitely large resistor The impedance is 100 Q viewed from here just like an endless cable Signal source Y 1009 100 Q network cable A termination resistor is connected to the end of the cable Fig 3 2 Actual Electric Signal Propagation Reference i d a a Teen matching Conversely impedance may be partially inconsistent which is called imped Impedance is usually kept consistent across the entire network which is called impedance ance mismatch ya TECHNICA Co LTD CUnet 4 How to Connect Termination Resistor This section describes how to connect a termination resistor specifically Figure 4 shows the connection of the termination resistor between the equipment with CUnet ICs Connect the termination resistor to both ends of the cable As shown in Figure 4 do not connect the termi nation resistor to the terminal that is in the intermediate position the halfway position in the network cable of a multi drop network 7 1009 network cable used The termination resistor is connected to both ends of the cable This is the signal source when Equipment the equipmenttransmits a packet with CUnet Z Driver 1009 Equipment with CUnet Receiver Receiver Driver This is the signal source when the equipmenttransmits a packet CUnetIC CUnetIC Fig 4 Termination in Half duplex Mode 10 TEP Technical Guide for Network ST ECHNICA CO
10. em failure or an unexpected error occurs the primary coil of the pulse transformer works as a simple copper wire and becomes equivalent to a DC load of 0 short circuited At this time the maximum current flows continuously from the dif ferential driver and the differential driver components produce heat Because of this conventional differential drivers have a thermal shutdown function Caution The cable lengths enabling signal transmission described in CUnet Introduction Guide and each CUnet IC Manual are based on our experimental measurements using differen tial driver components that operate on a power supply of 5 0 V The output of differential driver components operating on a power supply of 5 0 V is 5 0 Vp p whereas the output of differential driver components operating on a power supply of 3 3 V is 3 3 Vp p Thus the energy to supply signals to the network cables varies depending on the difference in the drive power supply of the differential driver components For this reason cable lengths enabling signal transmission are considered to vary depending on the energy to be supplied 8 2 Selecting Differential Receiver The differential receiver used in the HLS must meet the following requirements 1 Must have sufficient response capability to signals corresponding to the baud rate 2 Must have sufficient receiver sensitivity to signals mentioned above in 1 If the receiver sensitivity and response capabili
11. failure r occurs where the driver continuously drives the network all signal transmissions will cea 7 cease forcing the entire user system to stop Inductance depends on signals to be handled Since electromagnetic induction allows only high If used a pulse transformer never allows frequency signals to pass power components DC components to pass Therefore only _ Ue RC Canas Roo inoperable equipments fail to transmit sig Fig 9 1 Pulse Transformer nals having no adverse effect on other equipments 3 If external noise enters the network a pulse transformer prevents it from reaching receiver compo nents directly This results in an increased ability to guard against the external noise POS Our recommended pulse transformer is suitable for CUnet baud rates of 12 Mbps 6 Mbps Reference LR and 3 Mbps To get our recommended components refer to Web site at www steptechnica com Caution When using the CUnet at baud rates of 12 Mbps or more or 3 Mbps or less the user should select a suitable pulse transformer 16 EP T Technical Guide for Network ST ECHNICA CO LTD 9 2 Signal Transparency When Using Pulse Transformer When a pulse transformer suitable for baud rates is used it will be signal transparent Figure 9 2 shows a pulse transformer to be multi drop connected in the CUnet with signal transparency When connecting a termination resistor described in item 4 How to Connect Termination Resistor
12. for Network Preface This manual describes background information and technical briefings to helps in building a net work when using the CUnet Be sure to read CUnet Introduction Guide before understanding this manual Target Readers This manual is for e Those who first build a CUnet e Those who first use StepTechnica s various ICs to build a CUnet O Prerequisites This manual assumes that you are familiar with e Network technology e Semiconductor products especially microcontrollers and memory Caution e To users with CUnet User s Manual released before March 2001 Some terms in this manual have been changed to conform to International Standards e Some terms in this manual are different from those used on our website and in our product bro chures The brochure uses ordinary terms to help many people in various industries understand our products Please understand technical information on HLS Family and CUnet Family based on technical documents manuals E This manual has been prepared based on Standard English M meeting the requirements of the International Organization for Standardization ISO and the American National Standards Institute ANSI This English manual is consistent with the Japanese document STD CUTGN V1 1J e Standard English is a trademark of Win Corporation EP T STECHNICA Co LTD CUnet TEP Technical Guide for Network ST ECHNICA CO LTD CONTENTS 1
13. hort Avoid crossing between adjacent Equipment with CUnet Equipmentwith CUnet signals as muchas possible do not place components such as LSIs on the top or back of wiring X Fig 10 1 Connection between Equipments Using Two Modular Connectors Pa To other equipment To otherequipment When the connection and disconnection is enabled with a sub circuit board the equipment totherightis notseparated Equipmentwith CUnet Equipment with CUnet Ne Fig 10 2 Hot swap of Individual Equipments Using Sub circuit board 18 TEP STECHN ICA CO LTD Technical Guide for Network 11 How to Conduct Tests and Results Noise from environments surrounding a signal transmission system such as noise from other factory machines may result in malfunctions or damage to the signal transmission system used for control and mea surement In this case antinoise measures are taken at the design stage of a user equipment containing IC components However they provide only partial prevention because antinoise measures can only be taken to the point that does not affect signal propagation in cables and noise from surroundings cannot be removed completely Unblocked noise acts like a normal signal and is mixed with propagating signals resulting in garbage data or malfunctions Assuming this situation Step Technica conducted noise tests as shown in Figure 11 by injecting signal level noise into network cables This is
14. ork cable A network cable with these features inevitably has uniform impedance refer to 3 2 Actual Electric Signal Propagation A network cable is usually used in the CUnet Select the network cable suitable for the user system by con sidering factors other than signal transmission performance such as workability and simplicity of setting up the cable to connectors shielding fire resistance and strength etc In the CUnet a network with a relatively short cables about 10 m requires less emphasis on signal trans mission performance Signal transmission performance becomes more important as the cable length gets longer From this respect StepTechnica recommends using Ethernet LAN network cable 10BASE T Cate gory 3 or higher and shielded network cables The reason for using shielded network cable is to prevent interference from external noise static electricity Fig 7 Another reason is to prevent signal emission Fig 7 Single point grounding is generally preferable for shielding However the user system environment where single point grounding can be used is rare Therefore select the most effective grounding such as one side grounding both sides grounding midpoint grounding or non grounding according to the user s environ ment Guard against external noise Preventsignal emission as noise Equipment with CUnet Shielded network cable Tt a Ground shield Whether to ground one end or both end
15. s Schmitt input buffer receives waves at receiving point Hi from Lo Hi from Lo DARA PARA Lo from Hi Lo from Hi I I Clear signal with duty ratio of 50 Deformed signal with unbalanced duty ratio Fig 3 1 Propagation of Waves TEP STECHNICA CO LTD Technical Guide for Network 3 2 Actual Electric Signal Propagation Figure 3 2 shows actual electric signal propagation 1 A network cable can be compared to water with the same load weight impedance viewed from any direction The network cable with an impedance of 100 Q has an impedance of 100 Q viewed from any direction 2 If the end of the network cable is open the network cable is essentially the same as being connected to an infinitely large resistor just like a large wall When a propagated signal hits the infinite large resistor it is reflected 3 If the network cable is apparently endless signal reflection does not occur The network cable can be connected to a resistor termination resistor with the same value as the impedance of the network cable to create an electrical environment equivalent to an endless cable For these reasons in the network using CUnet network cables connect the termination resistor to the end of the network cable The impedance is actually 100 Q The impedance is unlimited as the cable viewed from any direction comes closer to the open end UN ae Y Y Y Y 100 Q network cable The open end is just like being connecte
16. s of the shield depends onthe user s system condition Shielded network cable Equipment with CUnet Fig 7 Shielded Network Cable Referente i The management function of network in the CUnet IC are useful in determining the oper io ability of the CUnet For details refer to the each CUnet IC Manual E ES CUnet 8 Howto Select Differential Driver Receiver Components This section describes how to select RS 485 differential driver receiver components used in the network TEP STECHNICA Co LTD 8 1 Selecting Differential Driver The following conditions must be satisfied when selecting the differential driver used in the CUnet 1 Driver responsibility based on baud rate For example with a baud rate of 12 Mbps the packet in the CUnet consists of 6 MHz and 3 MHz fre quency component signals Therefore when a normal clock with a high frequency component 6 MHz a square wave or a sine wave signal with a duty ratio of 50 is input to the input pin of the driver the output of a differential driver must have the capability to be driven similarly to the normal clock with a duty ratio of 50 2 Capability to drive cable impedance load If the driver operates on a power supply of 5 0 V it must have the capability to drive the network cable with an impedance of 100 Q at 50 mA 5 0 V 100 Q or more 3 Thermal shutdown function If the driver is enabled and a drive signal stops when a syst
17. twork cable composed of multiple twisted pairs in the CUnet do not connect the unused twisted pairs and twisted pairs in parallel Fig 6 Operational suitability tests conducted by StepTechnica show that handling unused twisted pairs by methods other than parallel connection keeping wires open or grounding them has no adverse effect on signals propagating through twisted pairs G N CUnet IC Differential driver receiver Keeping unused twisted pairs open or grounding them Each twisted pair has different twisting pitches Network cable composed of multiple twisted pairs Donotconnectin parallel Fig 6 Structure of Twisted Pairs and Handling Unused Twisted Pairs Reference The propagation speed of the signal in the twisted pair varies slightly depending on twist Poe ing pitch because the effective cable lengths are different Parallel connection of twisted pairs can cause signals with a time difference to be mixed at the terminal point causing transmission failure 12 TEP STECHNICA CO LTD Technical Guide for Network 7 Selecting Network Cable Various electric wires cables are available to feed power and transmit very small signals depending on the purpose Generally an electric wire with excellent signal transmission performance with smaller distribution quan tity faster signal propagation slower signal fade and less crosstalk interference between signals is used as a netw
18. ty to high frequency are insufficient in the differential receiver the values for network cable lengths described in CUnet Introduction Guide and each Man ual of the CUnet cannot be expected 14 TEP STECHNICA CO LTD Technical Guide for Network Our experience shows that there are some products where sufficient sensitivity and regen ARAE erative ability as described in the manuals or specification sheets provided by manufactur ers cannot be achieved The receiver used in the following two examples is described as 12 Mbps capable in the manual Example 1 RS 485 receiver sensitivity of 200 mVp p Manufacturer s manual described the receiver sensitivity as 200 mVp p However only frequency compo nent signals of less than 1 MHz could obtain this receiver sensitivity Example 2 Some products from manufacturer B require an input sensitivity of 3 0 Vp p to be able to regenerate a normal clock with a duty ratio of 50 when a 12 MHz normal clock is input Thus when selecting a differential receiver StepTechnica recommends the user conduct simple experiments Fig 8 for practical use of the CUnet For example when selecting a baud rate of 12 Mbps consisting of 6 MHz and 3 MHz frequency component signals connect the following signals to input pins of the differen tial receiver 1 6 MHz normal clock of less than 200 m Vp p a square wave and a sine wave signal with a duty ratio of 50 2 12 MHz
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