V.35 Technical Reference

V.35 Technical Reference_V.35 InterfaceV.35 has been around for quite some time. It was originally designed for a 48kbps synchronous modem - thats right, officially its top rated speed is 48kbps. However, V.35 has been used for many years in applications running from 20kbps up to and past 2Mbps. In 1989, CCITT BLUE BOOK (ITU) recommended the interface become obsolete and replaced it with the V.10/V.11 standard. However, V.35 still remains popular, and has evolved to using the specifications from V.11 for the differential signals, while the control signals remain unbalanced. The V.11/V.35 BLUE is fully interoperable with the old V.35 RED interface, except V.35RED may not handle the speed and distance of the newer spec. In many years of testing, I have not found any system, DSU/CSU, Router, Frame Relay bridge, etc. with incompatible V.35 interfaces. Most of the V.35 signals are for control and handshake purposes (like RTS, CTS, DSR, DTR) and these are implemented in unbalanced fashion, similar to RS232 / V.24. This approach is simple, inexpensive, and is usually adequate for these relatively invariant signals.V.35 gets its superior speed and noise immunity by using differential signaling on the data and clock lines. Unlike RS232 / V.24 which uses signals with reference to ground, V.35 receivers look for the difference in potential between a pair of wires. The wires can be at any potential, the signal is carried by voltage differences between the two wires. Now the secret; by twisting these two wires, it becomes likely that noise picked up on one wire will also be picked up on the other. When both wires pick up the same noise it has the affect of cancelling itself - as the same noise impulse on both wires is invisible to the receiver. Remember the receivers are only looking at the difference in voltage level of each wire to the other, not to ground. Many highspeed interfaces use this same technique, examples are: RS530, RS449, 10/100/1000baseT.The differential signals for V.35 are commonly labeled as either A and B. Wire A always connects to A, and B connects to B. Crossing the wires just inverts the data or clock. I have never seen any piece of equipment damaged from this, but they dont work this way, either._V.35 Signal DescriptionsNamePinDescriptionTypeFGAFrame/Chassis Ground-SGBSignal Ground-SDAPSend Data ADifferentialSDBSSend Data BDifferentialRDARReceive Data ADifferentialRDBTReceive Data BDifferentialRTSCRequest To SendUnbalancedCTSDClear To SendUnbalancedDSREData Set ReadyUnbalancedDTRHData Terminal ReadyUnbalancedRLSDFReceived Line Signal DetectUnbalancedTCEAUTransmit Clock Ext ADifferentialTCEBWTransmit Clock Ext BDifferentialTCAYTransmit Clock ADifferentialTCBAATransmit Clock BDifferentialRCAVReceive Clock ADifferentialRCBXReceive Clock BDifferentialLLJLocal LoopbackUnbalancedRLBBBRemote LoopbackUnbalancedTMKTest ModeUnbalanced-LTest PatternUnbalanced_V.35 Cable Design The design of your cable depends on what you are connecting together and the interfaces involved. There are two standard interface types Data Terminal Equipment (DTE) and Data Communication Equipment (DCE). Usually, but not always, the interface facing away from the network is the DCE, and the interface facing toward the network is the DTE. The DCE normally supplies the clock. All differential pairs must be twisted.DTE to DCEDTEDCEP-PS-SR-RT-RC-CD-DE-EH-HY-YAA-AAV-YX-XDTE to DTEThis cable design assumes that both devices provide their own transmit clock. Not all equipment does, in which case a modem eliminator with clock will be needed. If only one device has a clock you might be able to get away with using the one clock to drive transmit and receive in both devices. However, if it is the old type interface it probably wont work (the impedance will be too low).DTEDTEP-RS-TR-PT-SC-DD-CE-HH-EY & U-VW & AA-XV-Y & UX-W & AA_V.35 Interface DesignIt is important to remember that the CCITT (ITU) in 1989 recommended that V.35 RED is obsolete and recommended that the V.11 (RS422) interface be used for the differential interface. This makes the V.35 BLUE interface easier to design and better in performance. It also removes the need for a -5Volt power supply. I have built both the new and old V.35 interfaces and have found them to be fully compatible.V.35 Differential Driver The resistors Za and Zb are optional. I recommend 10Ohms to bring the interface to 50Ohms and to provide some protection from EMF. Here is a Tip: Note that the A or + signal is on the inverted output pin of the driver, most designers get this switched in their first design. This happens because some data books call the positive pin A and the negative pin B. The V.35 A or + must be the inverted pin. This is also true of the receivers.V.35 Differential ReceiverThe resistor Zt is optional. I recommend 150Ohms to reduce reflectance. However If you are trying to build a non intrusive receiver I would leave this out. Note this interface when left floating will have an unpredictable output. Some engineers place pull up (to pin A) and pull down (to pin B) resistors of 10K to provide a known state when the cable is unplugged or connected equipment is turned off.V.35 Unbalanced DriverThe typical driver is the standard RS232 driver 1488, however this requires + and - 12 Volts. Many of the new interfaces are using the V.24 / RS232 driver chips with the charge pump built in, so they only need +5V to operate. These come in many configuration some include both drivers and recievers.One of the typical isthe DS14C232 from TI or Max232.V.35 Unbalanced ReceiverThe typical IC used for the reciever is the 1489, it only requires 5 volts to operate, but mostnew designs are using the charge pump IC which haveboth the receivers and drivers in the same chip.V.35 Interface (some signals not shown)This shows a typical V.35 interface. A few signals like LT have not been included. The box is a M.34 connector set up in the DTE configuration._V.35 Breakout, Testing and ConversionADVICE manufactures unique products for working with the V.35 interface: V.35 Modify And Test Set - a V.35 breakout Universal Modify Test Set - a V.35/RS232/RS449/RS530 breakout and interface converter Exchanger - Interface converter (10permutations)The V.35 MATS and UMATS products allow you to make/break connections to diagnose and solve cabling connection problems. The V.35 MATS has a built in converter for monitoring the interface on a RS232 data scope. The UMATS and Exchanger allows conversion between many types of interface: V.35 to RS232 or RS449 or RS530.UMATS - Universal Modify And Test SetUMATSThe ADVICE UMATS is the ultimate tool for the data communication specialists or engineers tool bag. The UMATS combines the functionality of a breakout box and interface converter in a handy portable package. It can be battery powered, but comes with a wall-mount transformer for long-term installations or to bail you out when your battery gives up. The UMATS supports most current WAN communication interface standards, and has a bank of level shifters for converting between any pair of interfaces: V.35 can be converted to RS232, RS449 to RS422, or RS530 to V.35, etc. Each level shifter is also connected to a tri-state LED for convenient monitoring of signal levels.Standard Model Price: $625.00 US Includes: Jumpers 9V battery and AC adapter Soft case Instruction manual Quick reference card Free UPS ground shipping, Express shipping availableUMATS Manual International Model Price: $695.00 US Also includes: Universal power supply Free USPS shipping, Express shipping availableApplications Use like a breakout box to troubleshoot V.35, RS449, X.21, RS530, RS530A, V.11, V.24 cables and interfaces Use the interface conversion feature to adapt two devices with different communications interfaces Bridge the communication link between two devices in a null modem configuration Create a custom loopback for equipment testing Test the design of expensive cables before they are implementedFeatures M34 Connector (V.35) DB25 Connector (RS232, V.24, RS530, RS530A) DB37 Connector (RS449/RS422, V.11) All major signals are switched and have double termination to eliminate the need for daisy chain jumpers Test voltages available (0, +5, +10, -10) Eight tri-color LEDs to show status of selected signals Four balanced to unbalanced interface converters Four unbalanced to balanced interface converters 9 Volt battery for portable use. Wallmount AC transformer for long term or permanent use Each UMATS includes:o Jumperso 9V battery and AC adaptero Soft caseo Instruction manualo Quick reference card 1 year warranty on parts and laborSpecificationsConnectors Two DTE/DCE 34-M female V.35 Two DTE/DCE DB37-S female (RS449 - V.11 - X.21) Two DB25-S female (RS530 - RS232 - V.24)Converters/Level Shifters Converters meet RS422, V.11, RS530, RS232, V.24, X.21, and V.35 Blue Book specifications. Balanced to Unbalanced (protected by thermal shutdown) Each pair is tested at 6 Mbpso Input: Common Mode Range: +/- 14Vo Sensitivity: 200mVo Impedance: 1kOhmso Output: Common Mode Range: +/- 10Vo Max current: 10mA Unbalanced to Balanced (protected by thermal shutdown)o Input: Common Mode Range: +/- 25Vo Sensitivity: +/- 3Vo Impedance: 24kOhmso Output: Common Mode Range: 0 - 5Vo Maximum current: 150mA.Power Wallmount power unit: (UL/CSA) o Input: 120VAC, 60Hz, 3W o Output: 6VDC, 200mA Battery: 9V alkaline Dimensions 7.5 x 4 x 1.5 (19 x 10 x 4cm) 1.9lb (0.9kg) V.35接口在实际应用中主要用作N64Kbit/s（N=1-32）速率的数据业务接口，控制和选通信号为RS232电平，常用器件是ADM208；数据传送信号为RS422电平，常用器件为LTC1345。传输距离不超过15米。 对于LTC1345,数据传输速率可以达到4Mbit/s,保护电路如下图： 图中限流电阻选用R10欧姆（1/8W）保护器件选型为SM16LC05C对于ADM208，传输速率20Kbps,采用下面保护电路： 图中限流电阻选用100欧姆（1/8W）保护器件为ESDA14V2L对于目前的V.35接口在电路设计是采用多协议套片，在软件控制下，可满足V.24V.28V.35X.21等协议。由于不同协议接口的信号电平是不相同的（V.24最大，为12V），同时传输速率也是各不相同的（V.35最大，为4Mbit/s）。因此综合以上参数，保护器件应选择动作电压为12V以上的，结电容为80pF以下的保护器件An ITU standard (1968) for group band modems that combines the bandwidth of several telephone circuits to achieve higher data rates. Although not specified in the ITU standard, the V.35 connector has become a de facto standard for a serial interface in the 48 to 64 Kbps range. It is typically used between a modem and a multiplexor.V.35 ConnectorV.35 connectors are used for serial transmission between communications devices.认识V.24和V.35（个人了解到的，欢迎指点）V.24和V.35其实这2个东东指的是一种标准，或者为一种规程。如果说接口的话，应该说是V.24标准的接口或V.35标准的接口，但平时一般说是V.24接口或V.35接口。如果说其标准电缆的话，以此类推。这种标准定义了功能特性、过程特性、电气特性、机械特性（V.24建议未对机械特性作规定，使用ISO的标准，与ISO 2100兼容）。V.24基础知识在路由器中使用V.24的有WAN、AUX、8AS、Console符合标准的RS-232电平：12VV.24 电缆接口分 DCE 和 DTE 两侧，分别对应数据电路端接设备（网络侧）和数据终端设备（用户侧）。对应的 DCE 侧为插座（25 孔），DTE 侧为插头（25针）。通信的双方相对而言，路由器属于 DTE 侧设备，各种 Modem 、ISDN 终端适配器等则属于 DCE 设备。V.24 电缆在同步工作方式下的最大传输速率为：64000bps；异步工作方式下，最大传输速率为115200bps。符合 V.24 规程的接口及电缆在通信、计算机系统中使用的非常广泛，从计算机串口到路由器的广域网口，都有它的身影。在路由器上，主要出现在以下几种接口电缆之中： WAN 广域网接口 、AUX 备份接口、8AS 八异步串行接口、Console 控制台接口V.35基础知识控制信号遵从标准RS-232电平标准：12V数据与时钟遵从V.35电平标准：0.5VV.35 电缆的接口特性严格遵照 EIA/TIA-V.35 标准。路由器端为 DB50 接头，外接网络端为34 针接头，也分 DCE 和 DTE 两种，对应的 DCE 侧为插座（34孔），DTE 侧为插头（34 针）。V.35 电缆一般只用于同步方式传输数据，可以在接口封装 X.25、帧中继、PPP、SLIP、LAPB 等链路层协议，支持网络层协议 IP 和IPX。V.35 电缆通常用于路由器与基带 Modem 的连接之中，此方式下，与使用 V.24 电缆相同，路由器总是处在 DTE 侧。V.35 电缆传输（同步方式下）的公认最高速率是2048000bps（2Mbps）。与 V.24 规程不同，V.35 电缆的最高传输速率主要受限于广泛的使用习惯，虽然从理论上 V.35 电缆速率可以超过 2M 到 4M 或者更高，但就目前来说，没有网络营运商在 V.35 接口上提供这种带宽的服务。关于控制信号的基础知识以下是 V.24 及V.35 规程中几个常见然而重要的控制信号的说明：DTR（Data terminal ready，数据终端准备好）DSR（Data Set Ready 数据准备好）主要用于传输设备之间的协商信息。DCD（Data Carrier Detect 数据载体检测）用于设备检测当前的链路状态。RTS（request to send 请求发送）CTS（clear to send 清除发送）这些都是非常重要的数据流控信号，在很多接口规程中都可以看到。无论是在 V.24 还是V.35 接口规程中，这些控制信