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USB232U/485Ui

Page 17

Figure 4.2 RS422 Connected in Broadcast Mode

RS485 allows multiple (up to 32) unit loads to be connected in half duplex on a single twisted
wire pair for 'party line' type of communications as illustrated in Figure 4.3. A software method
must be used to stop more than one transmitter being on the line at any time. The circuit
design is such that no damage will be done to the transceivers if several transmitters are
turned on together.

See 5.2, ‘Half Duplex Transmission Turnaround’ for a discussion of the programming required
for controlling the transmission direction.

Figure 4.3 RS485 Connected in Multi-Drop, Half Duplex Mode

4.2.3.4 RS422/485 Bus Termination

For proper operation of the RS422/485 bus in full or half duplex, multi-drop or point to point
communication, it is recommended that termination be applied to the receiver end of the data
and control lines.

The simplest form of termination is line to line with typically a 120

Ω

across the differential

input, and this terminator is available on the USB485Ui interfaces, selectable by jumper JP1.

Terminator

Rx Resistor

Device n

Device 2

Device 1

A B

Tx

A' B'

Rx

A' B'

Rx

Terminator

Rx Resistor

USB485Ui

RS422 Port

Rx - A
Rx - B

Tx - A
Tx - B

A' B'

Rx

Terminator

Rx Resistor

Device n

Device 2

Device 1

A B

Tx/Rx

A B

Tx/Rx

Terminator

Rx Resistor

USB485Ui

RS485 Port

Rx - A'
Rx - B'

Tx - A
Tx - B

A B

Tx/Rx

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Содержание USB232U

Страница 1: ...ased product in a proper and efficient manner The information contained has been reviewed and is believed to be accurate and reliable however Amplicon Liveline Limited accepts no responsibility for any problems caused by errors or omissions Specifications and instructions are subject to change without notice USB232U 485Ui Instruction Manual Issue A2 Amplicon Liveline Limited Prepared by Helen Elco...

Страница 2: ...OAD STOCKPORT SK3 8LF UK We declare that the product s described in this Instruction Manual perform in conformity with the following standards or standardisation documents Electro Magnetic Compatibility EMC EMC Directive 89 336 EMC CE Directive 93 68 EEC David Cooper MIEE Director MEV Limited ...

Страница 3: ...n For Half Duplex Operation with Echo 7 2 3 1 3 Jumper Selection For Half Duplex Operation without Echo 7 2 3 2 Transmission Line Termination 8 2 3 2 1 Termination Resistors for RS422 485 Receivers 8 2 3 3 Jumper Factory Settings Summary 8 2 4 Application Software 9 2 4 1 Installation Testing 9 3 MAKING THE CONNECTIONS 10 3 1 External Connections 10 3 1 1 USB Connector 10 3 1 2 RS232 9 way Port 10...

Страница 4: ...ATION i A 1 1 USB i A 1 1 1 Series B connector i A 1 2 USB232U RS232 Port ii A 1 2 1 9 way Connector ii A 1 2 2 Data Rate ii A 1 2 3 I O Protection ii A 1 2 4 ESD Protection ii A 1 3 USB485Ui RS422 485 Port iii A 1 3 1 9 way Connector iii A 1 3 2 Data Rate iii A 1 3 3 Rx I P Termination iii A 1 3 4 Tx O P Protection iii A 1 3 5 I O Isolation iii A 1 3 6 ESD Protection iii A 1 3 7 Modes iii A 1 3 8...

Страница 5: ...Selection 8 Figure 2 5 Factory Jumper Setting Summary 8 Figure 3 1 USB Connector Termination Assignment 10 Figure 3 2 RS232 9 way Port Pin Designations 11 Figure 3 3 RS422 485 Amplicon Standard Port Pin Designations 11 Figure 4 1 Communications Standards Summary 16 Figure 4 2 RS422 Connected in Broadcast Mode 17 Figure 4 3 RS485 Connected in Multi Drop Half Duplex Mode 17 Figure 4 4 RS232 Loop Bac...

Страница 6: ......

Страница 7: ...the USB232U 485Ui Series of Data Communications Interfaces Each of the USB232U 485Ui series of interfaces is designed to meet stringent performance requirements and ease of use while maintaining compatibility with standard serial communications products USB 1 1 specification compliant Windows 98 2000 XP and Linux compatible Data rates selectable up to 1 M Baud RS232 and 3 M Baud RS485 FIFO modes s...

Страница 8: ... serial port designed to meet one of the following standards RS232 full duplex serial port furnished with a 9 pin D type male connector conforming to IBM practice The port is fully configured with two data six control I O lines and one signal return RS485 full duplex half duplex multi drop operation or RS422 full duplex without RTS CTS control lines Depending on the application RS485 or RS422 oper...

Страница 9: ...rom Amplicon Liveline Ltd contains 1 The USB serial interface as ordered in a protective bag The model will be one of the following and is identified by the type number printed on the PCB USB232U USB to RS232 Serial Communications Controller USB485Ui USB to RS422 485 Serial Communications Controller with I O signal isolation 2 The included distribution software and this manual on CD 3 Any addition...

Страница 10: ...ests you have conducted You may also be asked if the operating system prompted you for a disk when you installed the device 1 4 4 Repairs If the unit requires repair then please return the goods enclosing a repair order detailing the nature of the fault If the device is still under warranty there will be no repair charge For traceability when processing returned goods a Returned Materials Authoris...

Страница 11: ...USB232U 485Ui Page 5 Brighton East Sussex BN2 4AW England ...

Страница 12: ... Windows 2000 Windows XP or Linux 2 2 Installing the Interface Connect a USB Type B cable between the USB232U 485Ui serial communications device and the host computer When the device is physically connected to the PC the Windows 98 2000 or XP operating system will discover new hardware From then on respond to the questions asked When prompted for a disk use the disk supplied Exact installation ins...

Страница 13: ... the same serial lines 2 3 1 1 Jumper Selection For Full Duplex Operation Link Function JP2 2 3 JP3 2 3 Full Duplex 4 wire operation JP4 1 2 Receiver enabled when device is awake JP5 2 3 Transmitter enabled when device awake Figure 2 1 Jumper Settings For Full Duplex Operation 2 3 1 2 Jumper Selection For Half Duplex Operation with Echo Link Function JP2 1 2 JP3 1 2 2 wire operation TxA is connect...

Страница 14: ...P1 2 3 Data line NOT terminated Figure 2 4 Jumper Settings for Termination Resistor Selection Further notes on RS422 and RS485 operation are given later in Chapter 4 Using the Serial Communications Devices 2 3 3 Jumper Factory Settings Summary The USB485Ui interface can be reset to its factory defaults by re configuring the device according to the following tables Link Function JP1 1 2 Data Line T...

Страница 15: ...ce will operate in conjunction with all commercially available communications and data acquisition packages that support Windows 98 2000 and XP serial ports Install the required application software in accordance with the vendor s instructions assigning communications to the required COM port 2 4 1 Installation Testing Many applications packages include a self test feature and when the hardware an...

Страница 16: ...ector Termination Assignment 3 1 2 RS232 9 way Port Connections to the RS232 are made via 9 way D type connectors on the interface The on board connectors are male and the mating sockets are available as accessories Provision is made for securing by screw jacks The 9 way D type connector pin out conforms to the industry standard and will support commercially available cables and adapters 5 9 4 8 3...

Страница 17: ...Each connector is equipped with two or more different ground connections and care must be taken in the use of these grounds and the cable design to ensure that the EMC requirements are met and that isolation integrity is maintained in the case of the devices with isolated input output The connector pin out is such that commercially available cables and adapters are normally usable without modifica...

Страница 18: ...oltage appearing between this reference ground and the host PC USB ground is common mode and must not exceed the isolation voltage Connector Shell is not connected To maintain shield integrity a metal connector hood should be used which must be connected to the cable screen at the remote device 3 4 Choice of Cable As speeds and distances of communication increase the choice of cable over which the...

Страница 19: ...rs across the isolation barrier and not in series with the signal as would be the case if direct connection was employed The two ends of a link would normally have their grounds connected together through the signal ground line the protective ground line and or the cable shield Such a connection has an impedance such that an interfering signal caused by a difference in ground potentials is likely ...

Страница 20: ...d to support the common functions of RS232 and IBM and other manufacturers frequently adopt a 9 way D type connector that provides all the necessary functionality Where this 9 way system is used manufacturers conform to interface standard EIA 574 with the pin out configuration as shown in Figure 3 2 The RS422 interface is defined in the EIA TIA standard RS422 B Electrical Characteristics of Balanc...

Страница 21: ...Baud with decreasing cable length maxima at the higher rates At a signalling rate of 1 5 Mbaud by the USB485Ui the maximum cable length is specified as 80 m 260 ft see section 4 2 3 5 4 2 2 3 RS232 Cable Adapters With the variety of available interpretations of the RS232 interface it is often necessary to employ adapters or make up suitable cables to ensure that the proper connections are made The...

Страница 22: ...Gnd 250 mA to Vcc Receiver Input Resistance 3 kΩ to 7 kΩ 4 kΩ 12 kΩ Receiver Sensitivity 3 V 200 mV 200 mV Receiver Hysteresis 1 15 V 50 mV 50 mV Figure 4 1 Communications Standards Summary 4 2 3 2 RS422 485 Signalling Sense The RS422 and RS485 standards define the polarity of the signalling lines as follows The signaling sense of the voltages appearing across the interconnecting cable is defined ...

Страница 23: ... direction Figure 4 3 RS485 Connected in Multi Drop Half Duplex Mode 4 2 3 4 RS422 485 Bus Termination For proper operation of the RS422 485 bus in full or half duplex multi drop or point to point communication it is recommended that termination be applied to the receiver end of the data and control lines The simplest form of termination is line to line with typically a 120 Ω across the differenti...

Страница 24: ...ansmission line and appropriate techniques should be used for installation of the cables In a multi drop environment the cable should be looped through each device or if a spur is necessary the spur length should be kept to a minimum If screened cable is used some thought must be given to the connection of the screen shield This screen should not normally be used as a ground return for non isolate...

Страница 25: ...n the serial communication side of the interface and the following areas should be investigated Communication circuits For a communications circuit to operate correctly both ends of the circuit and the interconnecting cables must be serviceable and the correct connections made The vagaries of RS232 implementation often cause problems in making the proper connections and the manufacturers instructi...

Страница 26: ...S422 485 loop back testing The connections to be made are summarised in the following table No connection needs to be made to the ground pin Signal Function 9 way Amplicon From To Pin Pin Tx A Rx A 4 8 Tx B Rx B 5 9 Figure 4 5 RS422 485 Loop Back Test Connections Loop back testing is only appropriate to full duplex operation of the RS422 485 ports See Figure 2 1 for jumper settings 4 3 3 Loop back...

Страница 27: ...g Then click OK Modify the port settings to your requirement if required then click OK This will bring you to the main window and flashing cursor Now key presses will be echoed to the screen when the device and the loop back connection is correctly made For Linux a standard terminal application like minicom can be used instead of Hyper Terminal ...

Страница 28: ... this device supervises all transmissions by communicating with each of the Slaves in turn and offering it a transmission slot In token ring operation each device knows its ID neighbour and only talks directly to this next device Thus communication only occurs between adjacent pairs of devices and this makes for a flexible network but can be a more difficult method to implement In half duplex mode...

Страница 29: ... are three interfaces available in the range USB232U Communications RS232 I O Connector 9 way male D type with fixing screws USB485Ui Communications Isolated RS485 I O Connector 9 way male D type with fixing screws A 1 1 USB A 1 1 1 Series B connector 4 way series B connector Pinout to USB 1 1 input output standard The connector shell is connected to the USB chassis ground ...

Страница 30: ... USB232U port is configured as Data Terminal Equipment DTE A 1 2 2 Data Rate The port is capable of error free transmission at data rates up to 1 M Baud A 1 2 3 I O Protection Driver outputs and receiver inputs can be shorted beyond the RS232 fault limits to 30 V without damage A 1 2 4 ESD Protection The RS232 line input outputs have on chip protection from ESD transients up to 8 kV for human body...

Страница 31: ...e if the die temperature exceeds the limits A 1 3 5 I O Isolation For the isolated versions each RS485 interface is electrically isolated with no common connections to the other port Signal isolation is by opto couplers on the data lines and power to the drivers receivers is supplied through an isolated DC DC converter The design is such that it will sustain common mode voltages up to 75Vdc which ...

Страница 32: ...2 Data Bits Programmable 5 6 7 or 8 A 1 4 3 Stop Bits Programmable 1 or 2 A 1 4 4 Parity Programmable Even Odd or None A 1 5 PC INTERFACE A 1 5 1 Compatibility USB Bus revision 1 1 compatible A 1 5 2 Host resources Fully plug and play configurable A 1 5 3 USB Frame Rate 1 millisecond A 1 5 4 USB packet size 64 bytes A 2 SOFTWARE The distribution software is supplied on a CD ROM Windows 98 2000 and...

Страница 33: ...s Length 87 mm plus edge connectors Width 43 mm Height 26 mm A 3 1 2 Temperature Range Operating 0 C to 50 C Storage 20 to 60 C A 3 1 3 Power Requirements 5 VDC from USB Current required is less than one load unit 100 mA A 3 1 4 Dissipation Each device will dissipate less than 0 5 watts of heat ...

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