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DUAL- AND QUAD-PORT USB HUBS
Table 4-2. DIP-switch SW4 settings.
Switch Switch Port Description RS-485 RS-422
Setting Number
L SW4-1 1 TX+ to RX+ ON OFF
L SW4-2 1 TX- to RX- ON OFF
T SW4-3 1 Termination ON ON
PD SW4-4 1 1K Pull-Down ON OFF
PU SW4-5 1 1K Pull-Up ON OFF
L SW4-6 2 TX+ to RX+ ON OFF
L SW4-7 2 TX- to RX- ON OFF
T SW4-8 2 Termination ON ON
PD SW4-9 2 1K Pull-Down ON OFF
PU SW4-10 2 1K Pull-Up ON OFF
L = Loops TX+ to RX+ or RX- to TX- for two-wire operation.
T = Adds a 120-ohm termination resistor between RX+ and RX-.
PU = Pull-up. Adds a 1 K-ohm pull-up resistor to RX+.
PD = Pull-down. Adds a 1 K-ohm pull-down resistor to RX-.
Switch SW3 Settings
To select RS-485 mode (4-wire or 2-wire operation) or RS-422 mode (4-wire
operation), set the DIP switch labeled SW3 on the circuit board. (See Figure 4-2
and Table 4-3.)
Figure 4-2. RS-422/485 interface configuration.
NOTE
Switch positions SW3-1 and SW3-2 are for Port 1 and switch positions
SW3-3 and SW3-4 are for Port 2.
