Flowserve DDC-100 Modbus Direct-to-Host - Manual (Page 23)

40 DDC-100 Direct-to-Host Programming Guide FCD LMAIM4019-00 FCD LMAIM4019-00 DDC-100 Direct-to-Host Programming Guide 41
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5
Interfacing
Hardware for the
DDC-100 Network
The Flowserve Limitorque DDC-100 Network uses the RS-485 electrical standard for the network
communications medium. Because RS-232 ports are standard on most popular Host devices, Limi-
torque offers two RS-232 to RS-485 converters. These converters contain circuits that electrically
isolate the Host, improve noise immunity, and protect it from high-level voltage surges that may be
induced into the network.
RS-485 is used for the network electrical standard because it is capable of communicating data at
high rates over relatively long distances, and may be used in redundant loop or multi-drop network
topologies.
5.1 RS-232 to RS-485 Converters
Limitorque has sourced two models of the RS-232 to RS-485 converters. The primary distinction
between these models is self or auto-steering vs. steered as detailed in this section. The models
can be distinguished by the part numbers on the case of the converter. The specifications for both
models are given in Table 5.1. The dimensions of the converter enclosures are given in Figure 5.1
and the cable to connect the converter to a 25-pin serial port is shown in Figure 5.2.