User’s Manual
24 ECM-3610/3610L User’s Manual
3.7.7 Signal Description – Serial Port 2 – COM2 in RS-485 Mode (CM1)
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.
Warning: 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 (typ. 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.
3.7.8 Serial Port 1 with External DB9 Connector (CM2)
Signal PIN Signal
GND 5
9
RI
DTR 4
8
CTS
TxD 3
7
RTS
RxD 2
6
DSR
DCD 1
To Next Page
Loading...