User manual

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Figure 2.3: UNO-1140F Top View
2.2 COM1~COM4: RS-232/485 Interfaces
The UNO-1140/F offers four RS-232/485 serial communication interface
ports, and they are COM1 ~ COM4. Each port can be configured individ-
ually to either RS-232 or RS-485 by using on-board jumpers. Please refer
to A.2 for pin assignments. The default setting of each port are RS-232.
2.2.1 Automatic Data Flow Control Function for RS-485
In RS-485 mode, UNO-1140/F automatically senses the direction of
incoming data and switches its transmission direction accordingly. There-
fore 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.