SeaLevel ULTRA COMM+422.PCI User Manual page 11

Address and IRQ Selection
The ULTRA COMM+422.PCI is automatically assigned I/O addresses and IRQs by your motherboard BIOS.
Only the I/O addresses 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 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. Headers J1A – J4A allow the user to customize this interface
to their specific requirements. Each jumper position corresponds to a specific portion of the interface. If
multiple ULTRA COMM+422.PCI 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:
© Sealevel Systems, Inc. 7402 Manual | SL9063 7/2021
Name
Adds or removes the 1K ohm pull-down resistor in the RS-
P
422/RS-485 receiver circuit (Receive data only).
Adds or removes the 1K ohm pull-up resistor in the RS-422/RS-
P
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
Figure 6 - Headers J1A – J4A, Line Termination
Function
P T L L
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