16
DUAL- AND QUAD-PORT USB HUBS
Table 4-4. DIP-switches SW2 and SW4 settings.
Switch Switch Port Description RS-485 RS-422
Setting Number
L SW2-1 3 TX+ to RX+ ON OFF
L SW2-2 3 TX- to RX- ON OFF
T SW2-3 3 Termination ON ON
PD SW2-4 3 1K Pull-Down ON OFF
PU SW2-5 3 1K Pull-Up ON OFF
L SW2-6 4 TX+ to RX+ ON OFF
L SW2-7 4 TX- to RX- ON OFF
T SW2-8 4 Termination ON ON
PD SW2-9 4 1K Pull-Down ON OFF
PU SW2-10 4 1K Pull-Up ON OFF
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+ 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 SW1 and SW3 Settings
To select RS-485 mode (4-wire or 2-wire operation) or RS-422 mode (4-wire
operation), set the DIP switches labeled SW1 and SW3 on the circuit board.
(See Figure 4-4 and Table 4-5.)
