LDM485-P_LDM485-S_LDM485-PT_LDM485-ST调制解调器OMEGA

与光耦合器和电源直流-直流转换器完全隔离

工业浪涌保护器

六个LED诊断指示灯

3英里（5公里）时为19.2公里波特，0.5英里（0.8公里）时为57.6公里波特。

请求发送，清除发送握手

多点应用的三态输出，***多64个设备

连接器的选择

宽工作温度范围

无焊螺钉终端现场连接

LDM485-P_LDM485-S_LDM485-PT_LDM485-ST调制解调器OMEGA

LDM485是一款紧凑型RS-232至RS-485转换器，具有完整的电气隔离屏障和重型电气浪涌保护器。这些设备具有坚固的铝外壳，小到可以安装典型计算机设备的后面板，节省宝贵的办公桌和地板空间。光耦合器和直流-直流转换器提供隔离。RS-232连接通过公接头或母接头EIA 25针接头。RS-485的连接是通过方便的无焊螺纹端子实现的。

LDM485系列设计用于两线对上的全双工操作。输出是三态的，允许最多64个单元的多重下降。硬件握手可通过两个单独的线对进行。数据速率为直流至57.6K波特。提供六个诊断LED指示灯（见图1），用于安装指南和系统故障排除。RS-232接口支持请求发送、清除发送、数据设置就绪、接收线信号检测和数据终端就绪。为数据线提供了一个方便的零调制解调器开关。此外，线路终端开关将线路终端电阻和线路偏压电阻连接到RS-485接收线路。RS-485接口支持请求发送和清除单独的线对发送。LDM485可用于通过使用RTS和CTS电路作为第二个数据通道来转换两组发送和接收通道。数据速率相同。这些装置使用12伏交流电从壁挂式变压器拧入RS-485连接器上的端子1和2。或者，它们可以对RS-232连接器的插脚9（+）和10（–）使用±12Vdc。

LDM485符合EIA RS-232和RS-485规范。在LDM485可以传输数据之前，主机RS-232端口必须断言数据终端就绪。当没有断言数据终端就绪时，LDM485的所有输出都是高阻抗的，允许在公共通信电缆上多点连接多达64个LDM485单元。详见图1、图3。请求发送和清除发送作为两个单独的线对通过RS-485端口进行。这些可用于全双工流量控制。在LDM485可以传输数据之前，必须断言数据终端就绪（DTR）。这通常由主机完成。在主机设备不能提供DTR信号的情况下，可以使用RLSD自动断言DTR。在每个LDM485的RS-232接头P1上，只需将RLSD针脚8连接到DTR针脚20。此连接不适用于多点安装。

LDM485-P_LDM485-S_LDM485-PT_LDM485-ST调制解调器OMEGA

Complete Isolation with Optical Couplers and Power DC-to-DC Converter

Industrial Surge Protection Devices

Six LED Diagnostic Indicators

19.2K Baud at 3 Miles (5KM), 57.6K Baud at 0.5 Miles (0.8KM)

Request-to-Send, Clear-to- Send Handshake

Tri-State Outputs for Multidrop Applications, up to 64 Devices

Selection of Connectors

Wide Operating Temperature Range

Solderless Screw Terminal Field Connections

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 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 two-wire 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. 

The LDM485 conforms to EIA RS-232 and RS-485 specifications. Data Terminal Ready must be asserted by the host RS-232 port before the LDM485 can transmit data. When Data Terminal Ready is not asserted, all outputs of the LDM485 are high impedance, allowing up to 64 LDM485 units to be multidropped on a common communications cable. See Figures 1 and 3 for details. Request To Send and Clear To Send are carried through the RS-485 port as two separate wire pairs. These may be used for full duplex flow control. Data Terminal Ready, DTR, must be asserted before the LDM485 can transmit data. This is normally done by the host computer. For situations where the host equipment does not have the capability of supplying a DTR signal, RLSD may be used to automatically assert DTR. On the RS-232 connector P1 of each LDM485, simply connect RLSD pin 8 to DTR pin 20. This connection is not appropriate for multi-drop installations.