Specifications

Card Setup
Sealevel Systems ULTRA 530.PCI Page 5
Line Termination
Typically, each end of the RS-485 bus must have line terminating resistors (RS-422 terminates at the receive end
only). A 120-ohm resistor is across each RS-422/485 input in addition to a 1K ohm pull-up/pull-down combination
that biases the receiver inputs. Header E4 allows customization of this interface to specific requirements. Each
jumper position corresponds to a specific portion of the interface. If multiple ULTRA 530.PCI adapters are
configured in a RS-485 network, only the boards on each end should have jumpers T, P & P ON. Refer to the
following table for each position’s operation:
Name Function
P Adds or removes the 1K ohm pull-down resistor in the
RS-422/RS-485 receiver circuit (Receive data only).
P Adds or removes the 1K ohm pull-up resistor in the RS-422/RS-
485 receiver circuit (Receive data only).
T Adds or removes the 120 ohm termination.
L Connects the TX+ to RX+ for RS-485 two wire operation.
L Connects the TX- to RX- for RS-485 two wire operation.
P P T L L
Figure 7 - Headers E3, Line Termination