ES Range Product Manual
Version 2.9
© Copyright Brainboxes Limited 2013
Page 27 of 66
To open RS-422/485 settings:
1. Double click the port entry in Boost.LAN Manager
2. Go to the Port Settings tab
3. Click Advanced
4. Go to the RS-422/485 Settings tab.
5. The drop down list allows users to choose the desired RS-422/485 operations mode.
6. Select “RS-422 full duplex mode” for Full Duplex communications.
7. Select “RS-485 half duplex autogating mode” for Half Duplex communications.
Restore Defaults: Pressing this button will reset all settings on this Property Page back to the factory
defaults of this device. The default settings for this Property Page are “RS-422 full duplex mode”.
RS-485 Half Duplex Mode (ES-313, ES-320, ES-346 & ES-842 only)
For half-duplex operation, the transmit and receive lines of the port need to be connected together
making it a 2 wire system. This can be done by fitting the HD+ and HD- jumpers onto the headers
inside the ES device box.
Half-duplex links usually need biasing resistors fitted at some point on the link. These resistors are
used to hold the signal lines in a known state when the transmitters are off. If these resistors aren’t
used it is likely that random data will be received when no transmitter is turned on. This is because of
noise which is picked up along the cable which causes the lines to float to unknown states. The B+
resistor pulls the ‘+’ line up to 3V3 and the B- resistor pulls the other ‘– ‘line down to ground.
It doesn't matter which device on the link has them, as long as one of them does. Biasing resistors
can be connected by fitting the B+ and B- jumpers onto the headers on the ES device PCB.
The T jumper connects in a termination resistor. Termination resistors are used on the end devices in
the link to absorb the signal and stop echoes of the data being reflected back onto the transmission
line.
For point-to-point links (two devices linked), this should be fitted for both devices. For a multi-drop
bus (more than two devices linked on the same cable), the termination should be present at the two
end devices but not at any of the devices in between.
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