Advantech AIMB-250 user manual Serial Port 1 Connector in RS-485 Mode CN1, User’s Manual

				User’s Manual
2.4.10 Serial Port 1 Connector in RS-485 Mode (CN1)
	Signal	PIN	PIN	Signal
	DATA-	1	2	NC
	DATA+	3	4	NC
	GND	5	6	NC
	NC	7	8	NC
	NC	9	10	NC

2.4.10.1 Signal Description – Serial Port 1 Connector in RS-485 Mode (CN1)

Signal	Signal Description
	This differential signal pair sends and receives serial data to the communication
DATA+/-	link. The mode of this differential signal pair is controlled through the RTS
	register of Serial Port 2. Set the RTS register of the Serial Port 2 to LOW for
	transmitting, HIGH for receiving.

Do not select a mode different from the one used by the connected peripheral, as this may damage CPU board and/or peripheral.

The transmitter drivers in the port are short circuit protected by a thermal protection circuit. The circuit disables the drivers when the die temperature reaches 150 °C.

RS-422 mode is typically used in point to point communication. Data and control signal pairs should be terminated in the receiver end with a resistor matching the cable impedance (typical 100-120 Ω). The resistors could be placed in the connector housing.

RS-485 mode is typically used in multi drop applications, where more than 2 units are communicating. The data and control signal pairs should be terminated in each end of the communication line with a resistor matching the cable impedance (typical 100-120 Ω). Stubs to substations should be avoided.

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