HP AMD Geode ECM-5510 - Manual (Page 42)

ECM-5510
42 ECM-5510 User’s Manual
2.4.18 Serial 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
2.4.18.1 Signal 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.