© Sealevel Systems, Inc.
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ULTRA 530.LPCI User Manual
Figure 6 – Header E5, RS-485 ‘DTR’ Enabled, with No Echo
Address and IRQ selection
The ULTRA 530.LPCI is automatically assigned I/O addresses and IRQs by your
motherboard BIOS. Only the I/O address may be modified by the user.
Adding or removing other hardware may change the assignment of I/O addresses
and IRQs.
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
data 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.LPCI adapters are configured in an 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
P
Adds or removes the 1K ohm pull-up resistor in the RS-422/RS-485
receiver circuit
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.
Figure 7 - Header E4, Line Termination
