Avalue ECM-LX800D - Manual (Page 24)

ECM-LX800D
24 ECM-LX800D User ’s Manual
2.4.8.1 Signal Description – Serial Port Connector (JCOM2, JRS422/485)
Signal Signal Description
TxD
Serial output. This signal sends serial data to the communication link. The signal is
set to a marking state on hardware reset when the transmitter is empty or when
loop mode operation is initiated.
RxD Serial input. This signal receives serial data from the communication link.
DTR
Data Terminal Ready. This signal indicates to the modem or data set that the
on-board UART is ready to establish a communication link.
DSR
Data Set Ready. This signal indicates that the modem or data set is ready to
establish a communication link.
RTS
Request To Send. This signal indicates to the modem or data set that the on-board
UART is ready to exchange data.
CTS
Clear To Send. This signal indicates that the modem or data set is ready to
exchange data.
DCD
Data Carrier Detect. This signal indicates that the modem or data set has detected
the data carrier.
RI
Ring Indicator. This signal indicates that the modem has received a telephone
ringing signal.
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

). 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

). Stubs to substations should be
avoided.