LXI Wired Trigger Bus Extended Functin Revisin 1.0 8 Nvember 2016.
LXI WIRED TRIGGER BUS EXTENDED FUNCTION... 1 REFERENCE DOCUMENTS... 3 REVISION HISTORY... 5 1 OVERVIEW... 6 1.1 INTRODUCTION... 6 1.2 PURPOSE AND SCOPE OF THIS DOCUMENT... 6 1.2.1 Purpse... 6 1.2.2 Scpe... 6 1.3 DEFINITION OF TERMS... 7 1.4 ADDITIONAL LXI CONFORMANCE REQUIREMENTS... 8 1.4.4 Extended Functins... 8 2 PHYSICAL SPECIFICATIONS... 9 2.4 ELECTRICAL STANDARDS... 9 2.4.10 LXI Wired Trigger Bus Cnnectrs... 9 5 LXI DEVICE WIRED TRIGGER BUS...10 5.1 INTRODUCTION...10 5.2 RULE - LXI WIRED TRIGGER BUS CABLE AND TERMINATION SPECIFICATION....12 5.3 ELECTRICAL REQUIREMENTS...12 5.3.1 RULE Number f Channels...12 5.3.2 RULE Signaling Standard...12 5.3.3 RULE LXI Wired Trigger Bus Buffering...12 5.3.4 RULE M-LVDS Transceiver Type...12 5.3.5 RULE Input / Output Cnfigurability...12 5.3.6 RULE Drive Mde Cnfigurability...12 5.3.7 RULE Driver Tplgy...12 5.3.8 RULE Wired-OR Bias...14 5.3.9 RULE Wired-OR Bias Device...14 5.3.10 RULE Wired-OR Bias Device Functinality...14 5.3.11 RULE Pwer-up Default Cnfiguratin...14 5.3.14 RULE - Signal Ruting t All Eight Channels...14 5.3.15 RULE Simultaneus Transmit and Receive...15 5.3.16 Recmmendatin Gating f Unwanted Receiver Outputs...15 5.3.19 RULE Dcumentatin f Minimum Trigger Pulse Width...15 5.4 PHYSICAL REQUIREMENTS...16 5.4.1 RULE LXI Wired Trigger Bus Cnnectr Type...16 5.4.2 Recmmendatin LXI Wired Trigger Bus Cnnectr Type...16 5.4.3 RULE Number f LXI Wired Trigger Bus Prts...16 5.4.4 Permissin Additinal LXI Wired Trigger Bus Prts...17 5.4.5 RULE Trace Characteristic Impedance...17 5.4.6 RULE Printed Circuit Trace Lengths...17 5.4.7 RULE Channel-t-Channel Skew...17 5.4.8 RULE Maximum Stub Length...17 5.4.9 RULE LXI Wired Trigger Bus Cnnectr Pin Assignments...18 5.4.10 Recmmendatin +3.3V Prtectin Using Self-Healing Fuse...18 5.4.11 RULE Reserved Pins Shall Nt Be Used Fr Other Purpses...19 2
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Revisin histry Revisin Descriptin 1.0 Versin Initial Release Nvember 8, 2016 5
1 Overview 1.1 Intrductin The LXI Wired Trigger Bus (WTB) is a hardwired interface t specify input r utput cnfigurability, wired-or, and shielding and cabling fr the mst demanding triggering applicatins. This methd f triggering increases yur accuracy t the nansecnd range cmpared t sftware triggering via the LAN, which is typically in the millisecnd range. The LXI Device Wired Trigger Bus implements a cabling system t intercnnect multiple LXI Devices. The physical interface builds upn the TIA/EIA-889 Multipint Lw Vltage Differential Signaling (M-LVDS) standard. This standard uses differential current driven signals t exchange data between semicnductr devices. Each LXI Device supprting the LXI Wired Trigger Bus has a minimum f tw Trigger Bus cnnectrs. This prvides a pass-thrugh cnnectin f the bus by ruting signals thrugh each participating instrument. A terminatin device is required at the end f each LXI Wired Trigger Bus cnnectin segment, prvided by the LXI Wired Trigger Bus Terminatr. 1.2 Purpse and Scpe f this Dcument 1.2.1 Purpse Each LXI Extended Functin has its wn dcument with unique sectin numbering that, if merged with the LXI Specificatin Cre dcument, wuld prduce a cntiguus representatin f the entire LXI Specificatin.. This dcument specifies the requirements fr cnfrmance t the LXI Wire Trigger Bus Extended Functin. 1.2.2 Scpe This dcument defines a cmmn set f RULES and RECOMMENDATIONS fr cnstructing a cnfrmant LXI Device with ne r mre Extended Functins. Whenever pssible these specificatins use existing industry standards. The riginal LXI Device Specificatin included bth requirements fr all LXI Devices and a number f Extended Functins in a single dcument. Cmmn infrmatin mves t LXI Extended 6
Functin Cmmn Dcument and specific infrmatin related t the Extended Functin mve t separate dcuments. Therefre, t keep references t Sectin numbers, Rule numbers, Permissins, Recmmendatins, etc. the same as the riginal LXI Specificatin dcument, sme sectins are place hlders within this dcument and nly prvide a means t keep Rule and Sectins numbers the same as the riginal LXI Device Specificatin. 1.3 Definitin f Terms This dcument cntains bth nrmative and infrmative material. Unless therwise stated the material in this dcument shall be cnsidered nrmative. NORMATIVE: Nrmative material shall be cnsidered in determining whether an LXI Device is cnfrmant t this standard. Any sectin r subsectin designated as a RULE r PERMISSION is nrmative. INFORMATIVE: Infrmative material is explanatry and is nt cnsidered in determining the cnfrmance f an LXI Device. Any sectin r subsectin designated as RECOMMENDATION, SUGGESTION, r OBSERVATION is infrmative. Unless therwise nted examples are infrmative. RULE: Rules SHALL be fllwed t ensure cmpatibility fr LAN-based devices. A rule is characterized by the use f the wrds SHALL and SHALL NOT. These wrds are nt used fr any ther purpse ther than stating rules. RECOMMENDATION: Recmmendatins cnsist f advice t implementers that will affect the usability f the final device. Discussins f particular hardware t enhance thrughput wuld fall under a recmmendatin. These shuld be fllwed t avid prblems and t btain ptimum perfrmance. PERMISSION: Permissins are included t clarify the areas f the specificatin that are nt specifically prhibited. Permissins reassure the reader that a certain apprach is acceptable and will cause n prblems. The wrd MAY is reserved fr indicating permissins. OBSERVATION: Observatins spell ut implicatins f rules and bring attentin t things that might therwise be verlked. They als give the ratinale behind certain rules, s that the reader understands why the rule must be fllwed. Any text that appears withut heading shuld be cnsidered as descriptin f the specificatin. 7
1.4 Additinal LXI Cnfrmance Requirements 1.4.4 Extended Functins 1.4.4.1 General Descriptin The LXI Standard cnsists f the LXI Device Specificatin, required fr all LXI Devices. In additin, it includes all ptinal Extended Functins. LXI Extended Functins Extended Functins cme in the frm f external dcuments. Each Extended Functin dcument will have sectins numbered as thugh they were part f the LXI Device Specificatin, but the dcuments are separate t simplify maintenance f the standard and add new Extended Functins withut altering the LXI Device Specificatin. The Guide t LXI Dcumentatin identifies the Extended Functin dcuments. 1.4.4.2 Cnfrmance Requirements The rules in this dcument define the cnfrmance requirements fr this Extended Functin. In additin t the requirements fr all LXI Devices fund in the LXI Device Specificatin, an Extended Functin may require cnfrmance t anther Extended Functin. All these requirements are detailed in the fllwing Rule. 1.4.4.2.3 RULE LXI Wired Trigger Bus Cnfrmance Requirements LXI Device Specificatin Dcument: All LXI Devices shall cnfrm t the rules fund in Sectin 1.4 and all subsectins Sectins 3.5 and 3.7, including all subsectins Sectin 6.1.1, sectins 6.3 thrugh 6.4.2 including all subsectins, and 6.4.4 thrugh 6.4.6, including all subsectins Sectin 9.6 including all subsectins A Functin element with the FunctinName attributes f LXI Wired Trigger Bus and versin 1.0 in the LXIExtendedFunctin element f the LXI identificatin dcument as described by sectin 10.2.5 LXI Wired Trigger Bus Extended Functin (this Dcument): Include all rules 8
2 Physical Specificatins The LXI Device Specificatin details the physical requirements fr LXI Device cnfrmance. When adding the LXI Wired Trigger Bus, there are requirements added t the physical specificatin, as indicated belw in Sectin 2.4.10. 2.4 Electrical Standards 2.4.10 LXI Wired Trigger Bus Cnnectrs 2.4.10.1 RULE LXI Wired Trigger Bus Cnnectrs Fr devices incrprating the LXI Wired Trigger Bus, the number and type f LXI Wired Trigger Bus cnnectrs shall be as specified in Sectin 5. 2.4.10.2 Recmmendatin Cnnectr Lcatin Lcatin f the LXI Wired Trigger Bus cnnectrs shuld be n the rear panel f the device at the right hand edge as cnstrained by the lcatin f the pwer cnnectr. 2.4.10.3 Recmmendatin Cnnectr Orientatin The LXI Wired Trigger Bus cnnectrs shuld be vertically stacked with a minimum vertical, center-t-center, separatin f 11.05mm (0.435 inches). 2.4.10.4 Permissin Cnnectr Orientatin The LXI Wired Trigger Bus cnnectrs may be hrizntally munted immediately next t each ther. 2.4.10.5 Permissin Vendr-Specific Triggers Vendr-specific hardware trigger interfaces are permitted 9
5 LXI Device Wired Trigger Bus 5.1 Intrductin The LXI Device Wired Trigger Bus implements a cabling system t intercnnect multiple LXI Devices. The physical interface builds upn the TIA/EIA-889 Multipint Lw Vltage Differential Signaling (M-LVDS) standard. This standard uses differential current driven signals t exchange data between semicnductr devices. Each LXI Device supprting the LXI Wired Trigger Bus has a minimum f tw Trigger Bus cnnectrs. This prvides a pass-thrugh cnnectin f the bus by ruting signals thrugh each participating instrument. A terminatin device is required at the end f each LXI Wired Trigger Bus cnnectin segment, prvided by the LXI Wired Trigger Bus Terminatr. The terminatr attaches t the secnd cnnectr at each segment end, as seen in Figure 5.1. Figure 5.1 Cnfiguratin f LXI Devices using the LXI Wired Trigger Bus The LXI Wired Trigger Bus prvides eight physically independent trigger channels, matching the number f lgical channels prvided by the LXI Event Message mechanism in the LXI standard. The LXI Wired Trigger Bus designates LXI0 t LXI7, while the LXI Event Message designates identifiers LAN0 t LAN7. Trigger events made thrugh the LXI Wired Trigger Bus r the LXI Event Message trigger system are interchangeable, since the trigger mdel is cnsistent in each mde f peratin. Triggering within and between LXI devices varies widely between applicatins, and several examples f pssible trigger scenaris are as fllws: Internal r external events generate a trigger signal t initiate an actin in a device. A cmputer sends a trigger signal event that initiates an actin in a device. One device sends an LXI Event-based trigger signal t ne r mre ther devices. LXI Event-based triggers received by ne r mre devices cause hardware triggers t be sent t ne r mre ther devices A hardware trigger signal is time-stamped by a device and synchrnizes ther actins A cmmn reference clck, distributed using hardware trigger lines, synchrnizes actins in multiple devices. There are imprtant differences in perfrmance between the LXI Wired Trigger Bus and LXI Event Messages. LXI Event Messages are LAN-based and depend upn the LAN driver, LAN speed, sftware interrupts, and prcessr speed. The LXI Wired Trigger Bus is a dedicated bus interface with the fllwing characteristics: 10
Hardware delays n the bus cables and assciated ruting lgic dminate the trigger delay between an event and the initiatin f an actin at anther nde LXI Devices cnnect the trigger bus signals as directly as pssible frm the interface t the hardware perfrming the task. Once set up there is virtually n sftware r firmware related delays in reactin times. The LXI Wired Trigger Bus exhibits bth lw trigger delay and lw trigger jitter and perfrmance levels nt achievable thrugh the LAN based trigger mechanisms. In additin t supprting high perfrmance trigger peratins, the trigger bus can als exchange clck signals r ther data signals between LXI Devices. Each channel f the LXI Wired Trigger Bus is capable f perating in ne f tw mdes and set by prgramming the LXI Devices that are taking part in the trigger peratin fr that channel. LXI Devices that are nt taking part in a trigger peratin wuld have their LXI Wired Trigger Bus drivers disabled. The tw mdes f peratin are: Driven Mde. This prvides pint-t-multipint peratin. One device initiates a trigger event t ne r mre receiving devices. This mde uses ne driver per LXI Device fr each LXI Wired Trigger Bus channel. Wired-OR Mde. This is a multipint-t-multipint peratin. One r mre devices initiate a trigger event t ne r mre receiving devices. The Wired-OR Mde requires ne device t be the Wired-OR Bias Device, and its driver prvides a bias fr the LXI Wired Trigger Bus channel. Other devices participating in the wired trigger require the use f tw drivers fr each LXI Wired Trigger Bus channel, s they can bth transmit and receive their wn signals. The remainder f this sectin will fcus n the required peratin f LXI Devices that implement the LXI Wired Trigger Bus. Requirements related t the cnstructin f cables, prper terminatin, electrical adapter cmpnents, trigger distributin hubs, and physical device-t-device electrical perfrmance is lcated in the dcument LXI Wired Trigger Bus Cable and Terminatr Specificatins 11
5.2 RULE - LXI Wired Trigger Bus Cable and Terminatin Specificatin. Each LXI Device implementing the LXI Wired Trigger Bus shall meet the intercnnect requirements in the dcument LXI Wired Trigger Bus Cable and Terminatr Specificatins in rder t assure prper device peratin within a system cnsisting f ther LXI Devices implementing the LXI Wired Trigger Bus. 5.3 Electrical Requirements 5.3.1 RULE Number f Channels LXI Devices implementing the LXI Wired Trigger Bus shall supprt all eight hardware channels. 5.3.2 RULE Signaling Standard Each LXI Wired Trigger Bus channel shall use half-duplex, Multipint-Lw-Vltage-Differential Signaling (M-LVDS) with Type-1 receivers, cmpliant with TIA/EIA-899. 5.3.3 RULE LXI Wired Trigger Bus Buffering Each LXI Device cnnected t the LXI Wired Trigger Bus shall prvide half-duplex buffering n each channel, between the external M-LVDS pair and the internal signal ruting f the LXI Device. 5.3.4 RULE M-LVDS Transceiver Type One f the fllwing M-LVDS transceivers shall be used fr the LXI Wired Trigger Bus: Texas Instruments SN65MLVD080 (8 channel) r Texas Instruments SN65MLVD201 (single channel). 5.3.5 RULE Input / Output Cnfigurability Each LXI Wired Trigger Bus channel shall be individually cnfigurable as an input r utput (r bth), and shall be capable f being individually enabled r disabled. 5.3.6 RULE Drive Mde Cnfigurability Each LXI Wired Trigger Bus driver shall be individually cnfigurable t perate in either Driven r Wired-OR Mde. 5.3.7 RULE Driver Tplgy Each LXI Wired Trigger Bus driver shall cnsist f tw M-LVDS drivers with the utputs cnnected in parallel, as shwn in Figure 5.2b. In Driven Mde, nly ne driver shall be enabled, and the trigger signal shall be applied t the driver s input. In Wired-OR Mde, each driver shall be cnfigured t drive current frm the psitive (A) utput t the negative (B) utput when enabled, and the trigger signal shall be applied t the enable inputs f bth drivers. 12
Observatin Wired-OR Signaling In Driven Mde, nly ne f the tw parallel drivers is enabled, and the trigger signal is applied t the input pin f the enabled driver (the input t the disabled driver can be either high r lw). The differential trigger lines are driven t the high r lw state by surcing (psitive) r sinking (negative) current thrugh the terminatin resistrs. In Wired-OR Mde, bth parallel drivers are used with their input pins held high, and the trigger signal is applied t the enable pins f bth drivers. The differential trigger lines are driven t the high r lw state by surcing (psitive) r turning ff current t the terminatin resistrs (see Figure 5.2a). T imprve the nise margin, a single driver in ne f the cnnected LXI Devices (referred t as the Wired-OR Bias Device) can be prgrammatically cnfigured t drive a cnstant negative current thrugh the terminatin resistrs, thus frcing the trigger lines lw when all f the ther drivers n the bus are disabled. The parallel driver tplgy used in this mde is required t vercme the negative bias current, resulting in a net psitive current thrugh the terminatin. Nte that the Wired-OR Bias Device may still participate in Wired-OR signaling, but unlike all f the ther devices n the bus, it perates its driver in Driven Mde, rather than Wired-OR Mde. Cautin shuld be exercised when using a channel perating in Wired-OR Mde which has a Bias Device that participates in the Wired-OR signaling, particularly in applicatins requiring edge detectin. Under sme cnditins, it is pssible, due t nn-linear prperties in the drivers and the distributed nature f the bus, fr false pulses n the rder f 10-20 ns t be generated when the Bias Device changes state. In such situatins, depending n the applicatin, additinal steps may be required t prevent undesired behavir, such as deglitching the received signal using additinal lgic, re-sampling the bus 50-100 ns after an edge transitin, r by using reflectedwave switching. Nte that this effect des nt ccur in the mre typical situatin where the Bias Device is nt participating in the Wired-OR signaling, and thus shuld nly be f cncern in situatins where all f the devices n the bus are required t participate. The alternate Wired-OR tplgy shwn in Figure 5.2b may be advantageus when designing a printed circuit bard layut. In that tplgy, the inputs t the drivers have ppsite levels, and the psitive utput (A) f ne driver is cnnected t the negative utput (B) f the ther driver, and vice versa. This alternative tplgy is particularly advantageus if the driver IC s are placed n ppsite sides f the printed circuit bard, and each LXI Wired Trigger Bus channel uses ne driver frm each IC..01uF 50 50 + V _ 50 50.01uF Terminatr * * * * Terminatr Device 1 Device 2 Device 3 Device N (*See Fig 5.2b fr driver cnfiguratin) Figure 5.2 a) Single LXI Wired Trigger Bus Channel with Bus Terminatrs 13
Input D Driven DE A B + V _ VHI D Wired-OR A DE B + V _ Alternate Wired-OR A + D VHI V DE B _ VHI VLO VHI OR VLO D DE A B Input VHI D DE A B Input VLO D DE A B Figure 5.2 b) LXI Wired Trigger Bus Drivers, Driven and Wired-OR Mdes 5.3.8 RULE Wired-OR Bias Each LXI Wired Trigger Bus channel cnfigured fr Wired-OR Mde peratin shall be cnfigurable t receive a Wired-OR Bias by any ne f the LXI Devices cnnected t the bus. 5.3.9 RULE Wired-OR Bias Device Each LXI Device cnnected t the LXI Wired Trigger Bus shall be cnfigurable t act as the Wired- OR Bias Device fr any number f LXI Wired Trigger Bus channels cnfigured fr Wired-OR peratin. The Wired-OR Bias Device shall be capable f enabling and disabling the Wired-OR Bias under prgrammatic cntrl and n a channel-by-channel basis. Observatin Wired-OR Bias Device In the case where there are multiple channels cnfigured fr Wired-OR peratin, a single LXI Device can prvide the Wired-OR Bias fr all necessary channels, r the bias fr different channels can be prvided by different LXI Devices. In either case, the LXI Device prviding the bias fr a given channel is the Wired-OR Bias Device fr that channel. 5.3.10 RULE Wired-OR Bias Device Functinality The LXI Wired Trigger Bus driver f an LXI Device cnfigured t act as the Wired-OR Bias Device fr a particular channel shall always perate in Driven Mde. It shall drive the LXI Wired Trigger Bus channel lw (negative), unless it is participating in the Wired-OR cmmunicatin, in which case it shall actively drive the bus accrding t its input. (Refer t the Driven-Mde Driver schematic in Figure 5.2b). 5.3.11 RULE Pwer-up Default Cnfiguratin All LXI Wired Trigger Bus channels shall default t the disabled cnfiguratin when pwer is applied t the LXI device. 5.3.14 RULE - Signal Ruting t All Eight Channels Any LXI Device capable f transmitting r receiving signals n the LXI Wired Trigger Bus shall be capable f ding s n any f the eight LXI Wired Trigger Bus channels. 14
Observatin Signal Ruting t All Eight Channels This rule requires that any LXI Device using the LXI Wired Trigger Bus must be capable f ruting trigger signals t r frm any f the eight channels. This eliminates the pssibility f cnflicting channel use restrictins by different vendrs. 5.3.15 RULE Simultaneus Transmit and Receive LXI Devices using the LXI Wired Trigger Bus shall be capable f simultaneusly transmitting and receiving signals n any f the eight LXI Wired Trigger Bus channels. Observatin Transmitting and Receiving the Same Signal The ability f a device t receive its wn transmitted LXI Wired Trigger Bus signal is useful fr such purpses as diagnstics r trigger delay management. 5.3.16 Recmmendatin Gating f Unwanted Receiver Outputs In cases when it is nt pssible t disable individual receivers, unwanted receiver utput signals shuld be gated inside the LXI Device, using additinal lgic, t stp the input signal frm affecting internal trigger circuitry. Observatin Receiver Output Gating Functin When there is intentinal activity n an LXI Wired Trigger Bus channel that an LXI Device is nt currently using, the gating functin in the device is used t prevent that activity frm causing undesired device behavir. Furthermre, if n LXI Devices n the bus are actively driving a particular channel, the input signal levels f any receivers cnnected t it will lie very clse t their threshld levels. This cnditin can result in unintended receiver utput activity that shuld be gated inside the device. 5.3.19 RULE Dcumentatin f Minimum Trigger Pulse Width Manufacturers shall prvide dcumentatin specifying the minimum pulse width required by an LXI Device t achieve reliable triggering when using edge detectin. Observatin Waiting fr Trigger and Measurement Cmplete The Arm-Trigger State Machine discussed in Sectin 6, The LXI Prgrammatic Interface, f the LXI Extended Functin Cmmn dcument utlines the need t supprt Waiting fr Trigger and Measurement Cmplete, which are necessary t prvide synchrnizatin f this LXI Device with ther LXI Devices in the system. 15
5.4 Physical Requirements 5.4.1 RULE LXI Wired Trigger Bus Cnnectr Type 25-pin Micr-D cnnectrs shall be used t intercnnect LXI Devices incrprating the LXI Wired Trigger Bus. 5.4.2 Recmmendatin LXI Wired Trigger Bus Cnnectr Type The fllwing cnnectrs, r equivalents, are representative f the type recmmended fr LXI Wired Trigger Bus cnnectivity: ITT Cannn MDSM-25PE-Z10-VR17 (single cnnectr) r Mlex 83619-9011 (dual cnnectr). These cnnectrs can be duble-stacked in a 1U cnfiguratin fr efficient space utilizatin. Observatin Cnnectr Perfrmance While bth single and duble-stacked cnnectrs are acceptable, better perfrmance is achievable using duble-stacked cnnectrs, due t their cmpact size. 5.4.3 RULE Number f LXI Wired Trigger Bus Prts All LXI Devices implementing the LXI Wired Trigger Bus shall have at least ne LXI Wired Trigger Bus prt, cnsisting f a pair f LXI Wired Trigger Bus cnnectrs wired in parallel (likenumbered pins cnnected tgether). (See Sectin 2 fr recmmended cnnectr lcatins). 16
5.4.4 Permissin Additinal LXI Wired Trigger Bus Prts LXI Devices may have mre than ne LXI Wired Trigger Bus prt, prvided that each prt cnsists f a single pair f LXI Wired Trigger Bus cnnectrs wired in parallel (like-numbered pins cnnected tgether), and that each prt prvides the required buffering, as defined in Sectin 5.3.8. Observatin Additinal LXI Wired Trigger Bus Prts While it is permissible t have mre than ne LXI Wired Trigger Bus prt n an LXI Device, it is nt recmmended. Implement with cautin. Cnsider the fllwing pints fr additinal prts. a) Cunt each prt (cnnectr pair) n an LXI Device as a separate nde. This helps in determining the number f LXI Wired Trigger Bus ndes n a cnnectin pint. b) D nt assume the LXI Prgrammatic Interface supprts mre than ne LXI Wired Trigger Bus prt n an LXI Device. Cnsult the mst current versins f the fllwing LXI Cnsrtium dcuments befre implementing additinal prts: see Sectins 6 and 9 f this dcument and the IVI-3.15: IviLxiSync Specificatin. c) Perfrm tests n each prt individually t verify cmpliance with all f the requirements in Sectin 5 f the LXI Specificatin. d) Clearly identify the pairing f LXI Wired Trigger Bus cnnectrs t avid user cnfusin. 5.4.5 RULE Trace Characteristic Impedance Traces intercnnecting the LXI Wired Trigger Bus cnnectr pins shall be designed fr 100-hms (±10%) differential characteristic impedance. 5.4.6 RULE Printed Circuit Trace Lengths Traces intercnnecting the LXI Wired Trigger Bus cnnectr pins shall be kept as shrt as pssible, with a maximum trace length f 63.5 mm (2.5 inches) between cnnectrs. 5.4.7 RULE Channel-t-Channel Skew Inside the LXI Device, Traces intercnnecting the LXI Wired Trigger Bus cnnectrs shall be kept as equal in length as pssible, with a trace length difference between channels (maximum-tminimum) f less than 25 mm. Observatin Channel-t-Channel Skew This rule is included t ensure that the channel-t-channel timing skew intrduced by the LXI Device is less than 200 ps. 5.4.8 RULE Maximum Stub Length If a stub is created as a result f cnnecting the LXI Wired Trigger Bus t a transceiver, the maximum stub length shall nt exceed 12.7 mm (0.5 inches). 17
5.4.9 RULE LXI Wired Trigger Bus Cnnectr Pin Assignments LXI Wired Trigger Bus cnnectrs and cables shall use the pin assignments shwn in Table 5.1. 5.4.9.1 RULE +3.3V Supply n LXI Wired Trigger Bus Cnnectrs Each LXI Wired Trigger Bus cnnectr shall prvide +3.3 V (± 0.2 V), capable f surcing a ttal minimum current f 100 ma fr bth cnnectrs (nt 100 ma n each cnnectr). The pwer supply shall be shrt circuit prtected. Observatin +3.3V Supply Usage The +3.3V supply n LXI Wired Trigger Bus cnnectrs is useful fr such purpses as pwering vendr-specific adaptrs r ther similar devices. Nte that the +3.3V and +3.3V_RETURN pins are nt cnnected in LXI Wired Trigger Bus cables and are thus nly available directly frm the cnnectrs. 5.4.10 Recmmendatin +3.3V Prtectin Using Self-Healing Fuse It is recmmended the +3.3V pwer pin n each LXI Wired Trigger Bus cnnectr be prtected by a separate self-healing fuse. 18
5.4.11 RULE Reserved Pins Shall Nt Be Used Fr Other Purpses Pins designated as Reserved shall nt be used fr any purpse that is nt specifically authrized by the LXI Cnsrtium. Table 5.1 LXI Wired Trigger Bus Pin Assignments Pin Signal 1 +3.3V 2 +3.3V_RETURN 3 LXI1p 4 LXI1n 5 GND 6 LXI3p 7 LXI3n 8 GND 9 LXI5p 10 LXI5n 11 Reserved 12 LXI7p 13 LXI7n 14 LXI0p 15 LXI0n 16 Reserved 17 LXI2p 18 LXI2n 19 GND 20 LXI4p 21 LXI4n 22 GND 23 LXI6p 24 LXI6n 25 Reserved Cnnectr Shell CHASSIS Nte: LXI Wired Trigger Bus signals with a p suffix are the psitive (A) half f the pair and thse with an n suffix are the negative (B) half. 19