User manual

2 Introduction
possible to receive the data while they are sent out of the port. This option is named Echo, and it
can be deselected.
The transmitter for Tx lines in RS485 mode may be controlled by the application via RTS signal,
as well as by an internal automatic hardware circuitry.
Option Result
BIAS Polarize Tx+/Rx+ to +5V, Tx−/Rx− to GND
TxTerm 120Ω resistor from Tx+ to Tx−
RxTerm 120Ω resistor from Rx+ to Rx−
Figure 1: Serial Port Hardware Options
The modes of RS422 and RS485 allow to configure BIASing of the data lines, as well as connecting
120Ω termination resistors between the positive and negative wire. These three options can be
selected per port, they are disabled if the port is in RS232 mode.
2.2.1 VScom USB-COM PRO
Figure 2: VScom USB-COM PRO
Serial Ports 1
Connectors 1×DB9 male RS232, RS422, RS485 (6.1)
1×Terminal block RS422, RS485 (6.3)
Power Bus powered
FIFO size 128 Bytes Transmit
256 Bytes Receive
LED Power On Top: Red LED
2×Data On Top: Transmit Green, Receive Yellow
1×Mode On Top: 3-Color
Table 3: Features of VScom USB-COM PRO Single Port
June 2009 USB-COM PRO User Manual 7