Apollo ESP6000 User Manual

Page of 104
ECM-3612 
 
30 ECM-3612 User’s Manual 
 
 
2.3.6.1  Signal Description –Serial Port 3/4/1 Connector in RS-232 Mode (CM1, CM3, 
CM2) 
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.