User's Manual

Serial Port Operation
Crescendo UHF Half-Duplex User Manual Page 17 of 78
4.2 Configuration
Both main and auxiliary serial ports support the following configuration options:
 Baud rate: 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600 or 115200.
 Data bits: 7 or 8
 Parity: None, odd, or even
 Stop bits: 1 or 2
4.3 Advanced Features
4.3.1 Control Lines
The main serial port has four control lines:
 Ready to Send (RTS)
 Clear to Send (CTS)
 Data Terminal Ready (DTR)
 Data Carrier Detect (DCD)
The main serial port supports hardware flow control using the RTS and CTS control lines. When hardware
flow control is enabled:
 The radio will only transmit data to the DTE when the RTS line is high.
 The radio will raise the CTS line when its input buffer is less than three quarters full, and drop the
CTS line when its input buffer is at least three quarters full.
NOTE: When hardware flow control is enabled, the CTS line configuration is ignored.
In addition to hardware flow control, the CTS and DCD lines can be configured to behave in one of the
following ways:
 Always High: The control line is always held high.
 Always Low: The control line is always held low.
 Mirrors DTR: The control line mirrors the state of the DTR input.
 Mirrors RTS: The control line mirrors the state of the RTS input.
 Follows Rx Carrier: The control line goes high when a valid carrier is detected and goes low when
the carrier stops.
 Follows Tx Enable: The control line goes high when the transmitter is enabled and goes low when
the transmission is finished. This includes acknowledgements and retries when the radio is
operating in packet driven mode.
 Follows Online: The control line goes high if a packet addressed to the unit has been received. The
duration the control line stays high is set by the Online Timeout. The Online Timeout can be
configured between 100 and 65535ms. The control line also stays high while a connection is
established with a remote radio.
DTR is used to control Hayes dial-up connections (see section 6.5.5 on page 38)
Main -> Serial Port
Main -> Serial Port -> Settings