Model 285/365

RS-422/RS-485 To RS-232
Interface Converter

Reference Manual for Product:

0315-0134 Rev. F

Printed 11.13.02

1.0 General Description

The Model 285/365 Superverter is a unique interface converter that allows the user to operate in RS-232 to RS-422 or RS-232 to RS-485 mode. Furthermore, the RS-485 mode is selectable for two-wire or four-wire operation. The Model 285/365 comes equipped with a five-position dip switch to set the operating mode and a DTE/DCE switch. The Model 285 comes equipped with TD and RD LED's to verify operation while the Model 365 has the patent-pending DataSpy™ feature for installation and troubleshooting.

1.1 DataSpy™ Feature (Model 365 only)

Your new Telebyte product incorporates the patent-pending DataSpy™ feature, an LCD display designed to provide meaningful information to the user. It will assist in the initial installation and check out; thereafter it can be used as a performance monitor. In the case of a system problem, it provides information as to the status of the local link.

The Telebyte logo shown on the LCD display indicates the unit is powered. For power-stealing devices such as a converter, it is an indication that sufficient power is being applied to operate the device. The LCD display uses less than 1 milliWatt of power.
 

 
The data display on the LCD consists of graphical representations of TD (Transmit Data) and RD (Receive Data). Each of these signals is displayed the way a bit-change waveform would appear on an oscilloscope. Ordinarily, TD and RD are low or a minus voltage in the quiescent state. When data is transmitted, the transmit signal is brought high to a positive voltage. These two signal states are displayed on the LCD by either a low segment or a high segment. The low segment represents the minus voltage (the mark condition) while the upper segment represents a positive voltage (the space condition). The vertical bar connecting the lower segment to the upper segment is always on when power is applied.

If the transmit signal is in the quiescent state (continuously low) only the lower segments and the vertical bar will be illuminated. This indicates a constant negative state. If the transmit or receive inputs to the device were streaming, i.e., in the positive mode continuously, the LCD display would show the vertical segment and the upper segments only. For those cases where there is valid data transmission, both the upper and lower segments will be displayed simultaneously. A variation in display intensity between lower and upper segments will give the user a perception of the amount of data being transmitted.

The LCD display also shows the status of the following control signals: CTS, RTS, DSR, DCD, and DTR. These signals are displayed as mnemonic symbols, composed of three letters each, on the bottom line of the display. The presence of the three-letter mnemonic indicates that the respective control signal is high or positive. If the control signal is negative, the three-letter mnemonic is not displayed. For most full-duplex data-only converters, CTS and RTS are connected together while DSR, DCD, and DTR are connected together. The DataSpy™ LCD display will help verify correct operation.

2.0 Specifications

2.1 Interface

Conforms to EIA RS-232, RS-422 and RS-485 specifications.

2.2 Connectors

2.2.1 Model 285 RS-232 : DB25M.

2.2.2 Model 365 RS-232 : DB25M or F (as ordered)

2.2.2 Both Models RS-422/RS-485 : Five-position terminal block.

2.3 Data Rate

2.3.1 Model 285 : 0 to 64 KBPS

2.3.2 Model 365 : 0 to 115 KBPS

2.4 Switches

DTE/DCE switch for reversing TD & RD. Five-position dip switch: set RS-485 to two or four wire, RS-422 and termination.

2.5 Indicators

Model 285 : TD and RD LED's

Model 365 : Equipped with an LCD display for data, five control signals and power.

2.6 Power

115VAC @ 60 Hz (220 VAC @ 50 Hz optional). See section 7.0, "Power," for more options.

2.7 Size

Model 285 : 2" W x 3.5" L x 0.875" H (50.8mm x 88.9mm x 22.2mm)

Model 365 : 2" W x 4.15" L x 0.79" H (50.8mm x 105.4mm x 20.1mm)

2.8 Environment

0^o to 50^o C, 5% to 95% relative humidity.  

3.0 Installation

The Model 285/365 is designed to interface RS-232 with RS-422 four-wire, RS-485 four-wire or RS-485 two-wire. In addition, the RS-485 mode can be set to have its transmitter enabled by RTS or can be set to sense when data is being transmitted by the RS-232 device. The user also has the ability to enable a 220-Ohm terminator when the Model 285/365 is configured in the two-wire mode. To set the dip switches select the option from the following chart.
  

X = Enable (ON) / Disable (OFF) 220-Ohm Terminator

 
Note: The 220 terminator should only be selected for use in RS-485 two-wire options.

In addition to setting the five-position dip switch, the user must also determine if the Model 285/365 will be configured as a DCE or a DTE device. When configured as a DCE device, the Model 285/365 will connect to a DTE device such as a PC or terminal. When set as DTE device, it will connect to a DCE device such as a modem.

The Model 365 has built-in protection to help prevent damage to the unit from surges. The surge suppression is connected internally to Frame Ground, Pin 1, and Signal Ground, Pin 7. This connection provides a path for the discharge of the surge. If the equipment does not support Frame Ground then the terminal marked "G" can be connected to an external earth ground connection.  

4.0 Operation

RS-422: When the Model 285/365 is configured as an RS-232 to RS-422 converter it will perform full-duplex conversion of the TD and RD signals. The RS-422 equipment is connected to the Model 285/365 through the five-position terminal block marked "G," "R-," "R+," "T-," and "T+." R+ and R- identify the receiver inputs into the unit and T+ and T- identify the transmitter outputs. When connecting the unit to other RS-422 equipment, the T+ and T- should be one twisted pair while R+ and R- should be another. The G connection is connected to Pin 1, Frame Ground, on the RS-232 port.

RS-485: In the four-wire mode the Model 285/365 receiver is always ON and the transmitter can be controlled in one of two ways. In the first method, the transmitter can be enabled when the RTS (or CTS) is enabled or goes high. The second method is to turn the Transmitter ON when data is applied to the Model 285/365 from the RS-232 device. Connection to the Model 285/365 is made to the terminal block with T+ and T- being the transmit pair and R+ and R- the receive pair. When operating in the four-wire mode, T+ and T- should be one twisted pair and R+ and R- another twisted pair.
 

The RS-485 two-wire mode uses one twisted pair to transmit and receive. The Model 285/365 will normally be in the receive mode or waiting for data from the RS-485 equipment. When the unit wants to transmit, it uses RTS or waits for data from the RS-232 to enable its transmitters, depending on the mode it is set for. The Model 285/365 uses the T+ and T- for its connections to the RS-485 device.

5.0 Troubleshooting

The following is a list of possible problems that may arise during the installation and solutions to these problems:

1. The data being received is garbled.

1.  The DTE/DCE switch is not set properly (see section 3.0, "Installation"). On the Model 365, observe the LCD and verify that TD and RD are shown as low in the quiescent state (see Section 1.1, "DataSpy™ Feature").

2.  The equipment that the Model 285/365 is connected to does not have the communication parameters set the same.

3. T+ and T- are reversed going to R+ and R-. On the Model 285 look at the RD LED; if it is ON continuously then the leads are reversed. On the Model 365 look at the LCD and if RD is shown as a constant high or streaming  (see Section 1.1, "DataSpy™ Feature") then the wires are reversed (T+ goes to R+ and T- to R-).

4. One of the four wires is broken.

5. Wires are not paired properly: T+ and T- should be one twisted pair and R+ and R- should be the other.

2. No data is being received.  

1. The customer equipment is not connected to the Model 285/365.
2. The DTE/DCE switches are not set properly (see section 3.0,"Installation"). On the Model 365, observe the LCD and verify that TD and RD are shown as low in the quiescent state (see Section 1.1, "DataSpy™ Feature").
3. One or more wires between the modems are open.
4. The link connection exceeds the maximum specified distance.
    

If the unit is believed to be defective, operation can be verified if one of the devices to which the modem is attached is capable of operating in a full-duplex mode (e.g., a terminal or a PC using a communications package such as Procomm). Connect the Model 285/365 to the terminal through the RS-232 connector and make the following loopback connections at the analog interface.

T+ to R+ and T- to R-

If the modem is functioning correctly, any data entered on the keyboard should appear on the screen.
 

6.0 RS-232 Pin Number Assignments

 
* These signals can be reversed using the selector switch.
**, *** Connected together.
 

7.0 Power

7.1 Model 285

The Model 285 is powered by a small, wall-mounted transformer that supplies 9 VAC @ 500 mA. The transformer must be connected to the Model 285, through the 3.5mm connector located on the side of the unit, before plugging the transformer into the wall.

7.2 Model 365

The Model 365 is powered by a small, wall-mounted power supply that provides 12 VDC @ 500 mA. The power supply must be connected to the Model 365, through the 1.3mm connector located on the side of the unit, before plugging the power supply into the wall.

Note: Both of these units can be powered from +12 VDC on Pin 9 of the DB25 connector and Ground on Pin 7.