Procom Converter RS485 - Manual (Page 2)

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Chapter 2 GETTING STARTED
POWER REQUIREMENTS:
The RS232/RS485 Converter can be powered using any voltage less than 32 volts. The converter
consumes 75 mA. From the converter, a 6 wire line carries the data to and from the remote stations. Two
wires send data, two wires receive data, one additional line is connected to the computer's ground and one
wire is connected to the power supply input (before the converter's voltage regulator). This way,
unregulated power can be carried to the remote stations.
The RS232/RS485 converter is NOT optoisolated. Optoisolation must be provided independently in each
station along the network as is the case with the RS485 Data Acquisition and Control line of boards.
LINE CONNECTIONS AND TERMINATION:
The 6 wire link can be brought to the on-board telephone jack (RJ11) or to the 6 position terminal strip
thus allowing the use of any type of wire for the link.
Figure 1.
When connecting to the terminal strip, data is transmitted via the terminal strip lines marked YELLOW
and BLUE in Figure 1, whereas data is received via the BLACK and WHITE lines. The line must be
terminated by a resistor network which is placed across the 2 pairs of data wires. For this, a non-bussed,
14 or 16 pin resistor network is required. (The pin-out is not important since the only 2 resistors used are
the ones at the centre of the network). Using a resistor network allows the placement of different
resistance values. 120 Ohms is recommended, but in fact, the resistance should match the impedance of
the data transmission line.
IMPORTANT: For optimal operation, a data network requires termination on both ends of the link. This
means that intermediate stations need NOT be terminated with resistors (if you are using the RMV RS485
TERMINAL STRIP RJ11
JUMPERS