Com3 ~ Com4: Isolated 5-Wire Rs-232/ 422/485 Interfaces; Table 2-1: Serial Ports Default Setting - Advantech UNO-2050 User Manual

2.3 COM3 ~ COM4: Isolated 5-wire RS-232/
422/485 Interfaces
The UNO-2050 offers two isolated 5-wire RS-232/422/485 serial
communication interface ports, and they are COM3 and COM4. The
connector type of COM3 and COM4 is screw-terminal block that it's
easy for wiring without additional daughter board. Each port can be
configured individually to either RS-232, RS-422 or RS-485 by using
on-board jumpers (see Appendix A.3), and Table 2-1 lists the default
setting of each port.
16C954 UARTs with 128-byte standard
Advantech UNO-2050 comes standard with Oxford OX16PCI964
UARTs containing 128 bytes FIFOs. These upgraded FIFOs greatly
reduce CPU overhead and are an ideal choice for heavy multitasking
environments.
Automatic Data Flow Control Function for RS-485
In RS-485 mode, UNO-2050 automatically senses the direction of
incoming data and switches its transmission direction accordingly.
Therefore no handshaking signal (e.g. RTS signal) is necessary. This
feature lets you simply and quickly build an RS-485 network with just
two wires. More importantly, application software previously written
for half duplex RS-232 environments can be maintained without need
for modification.
IRQ and Address Setting
The IRQ and I/O address range are both assigned by BIOS. COM3,
COM4 serial ports and on-board digital I/O use the same IRQ.

Table 2-1: Serial ports default setting

COM Port
COM3
COM4
Default Setting
RS-485
RS-485
Chapter 2 Hardware Functionality 1 1