ECM-5510

2.4.18Serial Port 2 Connector in RS-485 Mode (CN6, Pin 11-20)

 

Signal

PIN

PIN

 

Signal

 

DATA+

11

12

 

NC

 

DATA-

13

14

 

NC

 

 

 

 

 

 

 

GND

15

16

 

NC

 

NC

17

18

 

NC

 

 

 

 

 

 

 

NC

19

20

 

NC

 

 

 

 

 

 

2.4.18.1Signal Description – Serial Port 2 Connector in RS-485 Mode (CN6, Pin 11-20)

Signal

Signal Description

 

 

DATA+/-

This differential signal pair sends and receives serial data to the communication 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.

42 ECM-5510 User’s Manual