LDM485

LDM485 Fully Isolated Limited Distance Modem, RS-232/485 Converter Description The LDM485 is a compact RS-232 to RS-485 converter which features a complete electrical isolation barrier and heavy duty electrical surge protectors. These devices feature a rugged aluminum enclosure small enough to mount on the back panel of typical computer equipment, saving valuable desk and floor space. Isolation is provided by optical couplers and a DC-to-DC converter. The RS-232 connection is through male or female EIA 25-pin connectors. The RS-485 connections are made through convenient solderless screw terminals. The LDM485 series is designed for full duplex operation over twowire pairs. Outputs are tri-state, allowing multidropping of up to 64 units. Hardware handshake is available over two separate wire pairs. Data rates are DC to 57.6k baud. Six diagnostic LED indicators are provided (see Figure 1) for installation guidance and system troubleshooting. The RS-232 interface supports Request To Send, Clear To Send, Data Set Ready, Received Line Signal Detect, and Data Terminal Ready. A convenient null modem switch is provided for the data lines. Also, a line termination switch connects a line termination resistor and line bias resistors to the RS-485 receive lines. The RS-485 interface supports Request To Send and Clear To Send on separate wire pairs. The LDM485 may be used to convert two sets of send and receive channels by using RTS and CTS circuits as the second data channels. Data rates are the same. The units use 12VAC from a wall-mounted transformer to screw terminals 1 and 2 on the RS-485 connector. Alternately, they can use ±12VDC to pins 9 (+) and 10 (–) of the RS-232 connector. Features Á COMPLETE ISOLATION WITH OPTICAL COUPLERS AND POWER DC-TO-DC CONVERTER Á INDUSTRIAL SURGE PROTECTION DEVICES Á SIX LED DIAGNOSTIC INDICATORS Á 19.2K BAUD AT 3 MILES (5KM), 57.6K BAUD AT 0.5 MILES (0.8KM) Á REQUEST-TO-SEND, CLEAR-TO-SEND HANDSHAKE Á TRI-STATE OUTPUTS FOR MULTIDROP APPLICATIONS, UP TO 64 DEVICES Á SELECTION OF CONNECTORS Á WIDE OPERATING TEMPERATURE RANGE Á SOLDERLESS SCREW TERMINAL FIELD CONNECTIONS Dataforth does not authorize or warrant its products for use in life support/critical applications. Model Channel Lines Control Lines (2) LDM485 TD, RD, RTS, CTS RTS, CTS, DTR, DSR, RLSD 1 (Reverses RS-232 pins 2 and 3) 60mA max/output 12kΩ min/input 12VAC, ±10%, 10W screw terms 1 & 2 +11.5 to +17VDC @ 500mA on pin 9 -11.5 to -17VDC @ 100mA on pin 10 0°C to +70°C, 0-95% relative humidity, noncondensing 6.6 in x 2.1 in x 1.28 in (167.6 mm x 53.3 mm x 32.5 mm) 7 oz (200 g) max 11.0 oz (311.8 g) max >100,000 hrs (2) Null Modem Switch RS-485 Output Drive RS-485 Input Impedance Specifications Model Baud Rate Range Baud Rate Distance (miles)(1) Distance (km) Wire Capacitance Maximum Multidrop Units Common Mode Isolation Differential Mode Surge Protection (9 devices) Modes 0 – 57.6K 57.6K 38.4K 19.2K 0.5 1 3 0.8 1.7 5 9.6K 4.8K 2.4K – 0 4 5 8 6.7 8.3 13.3 LDM485 Power: AC operation(3) DC operation Operating Environment Dimensions Weight PT3, PT3E MTBF(4) Equal to 25pF per foot and up to 32 multidrop units 64 Surge: 1500V Continuous: 1000V (AC input) ANSI/IEEE C37.90.1-1989 (all RS-485 inputs and outputs) Asynchronous 4-wire duplex, 2-wire half-duplex, 2-wire simplex Notes: (1) Distances reduced if multidropping more than 32 units; by 30% for 33-48 units, 50% for 4964. (2) TD = Transmit Data, RD = Receive Data, RTS = Request To Send, CTS = Clear To Send, DTR = Data Terminal Ready, DSR = Data Set Ready, RLSD = Received Line Signal Detect. (3) 120VAC and 220 VAC power transformers are available. (4) Ground-benign environmental conditions (no salt atmosphere,