Typical settings for Serial Port 3 configuration options are shown below:
Switch
Pin
RS485 4 Wire
RS485 2 Wire
J4
N/A
Connect pins 1 and 2
Connect pins 2 and 3
SW2-1
T
2
ON
ON
SW2-2
PU
2
ON
ON
SW2-3
PD
2
ON
ON
SW2-4
L
OFF
ON
SW2-5
L
OFF
ON
Switch Name
Function
1
T
Adds or removes the 120 ohm termination.
2
PU
Adds or removes pull-up resistor in the RS-485 receiver circuit
3
PD
Adds or removes pull-down resistor in the RS-485 receiver circuit
4
L
Connects the TX+ to RX+ for RS-485 two-wire operation.
5
L
Connects the TX- to RX- for RS-485 two-wire operation.
2
Termination, Pull-Up and Pull-Down may not be necessary depending on the equipment to which the R4
Port 3 is connecting.
©Sealevel Systems, Inc.
R4 Manual
16
SL9260 06/2015
