20
DUAL- AND QUAD-PORT USB HUBS
Table 4-7 (continued). DIP-switches SW2 and SW4 settings.
Switch Switch Port Description RS-485 RS-422
Setting Number
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 4-6 and Table 4-8.)
Figure 4-6. RS-422/485 interface configuration.
NOTE
Switch positions SW3-1 and 2 are for Port 1, and switch positions SW3-3
and 4 are for Port 2. Switch positions SW1-1 and 2 are for Port 3, and
switch positions SW1-3 and 4 are for Port 4.
