7
UNO-2184G/2174G/2174GL User Manual
Chapter 2
H
ardware
F
unctionality
2.2.1
RS-232/422/485 Interface (COM 1 ~ 2)
The UNO-2184G/2174G/2174GL offers 2 RS-232/422/485 serial communication
interface ports: COM1 and COM2. Please refer to Appendix A.4 for their pin assign-
ments. The default setting of COM1 and COM2 are RS-422/485.
2.2.2
16C550 UARTs with 128-byte Standard
Advantech UNO-2184G/2174G/2174GL comes with OXuPCI952 UARTs containing
128 bytes FIFOs. These upgraded FIFOs greatly reduce CPU overhead and are an
ideal choice for heavy multitasking environments.
2.2.3
RS-422/485 Detection
In RS-422/485 mode, UNO-2184G/2174G/2174GL automatically detects signals to
match RS-422 or RS-485 networks (No jumper change required).
2.2.4
Automatic Data Flow Control Function for RS-485
In RS-485 mode, UNO-2184G/2174G/2174GL automatically detects the direction of
incoming data and switches its transmission direction accordingly. No handshaking
signal (e.g. RTS signal) is necessary. This lets users conveniently 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 modification.
2.3
RS-232/422/485 Selection
COM1 and COM2 support a 9-wire RS-232/422/485 interface. The system detects
RS-422 or RS-485 automatically for COM1 and COM2.
You can set the “Auto Flow Control” mode of RS-485 or “Master/Slave” mode of RS-
422 by using the external switch for COM1 and COM2.
Note!
In S1 mode, COM 1 and COM 2 data re-transmission will not function
properly and may include error signals after wake up.
SW3
Note
Function
Pin1
Pin2
Pin3
ON
ON
ON
Disable COM1
ON
ON
OFF
COM1 RS232
RS232
ON
OFF
ON
COM1 RS485
RS485
ON
OFF
OFF
COM1 Slave Mode RS422 (Default)
RS422+RS485
OFF
ON
ON
COM1 RS485 with Termination
RS485
OFF
ON
OFF
COM1 Slave Mode RS422 with Termination
RS422+RS485
OFF
OFF
ON
COM1 Master Mode RS422
RS422
OFF
OFF
OFF
COM1 Master Mode RS422 With Termination RS422
