User's Manual

455U Radio Modem Module User Manual
Page 18 © November 2004
Chapter Three OPERATION
3.1 Power-up and Normal Operation
When power is initially connected to the 455U module, the module will perform internal
diagnostics to check its functions. The following table details the status of the indicating
LEDs on the front panel under normal operating conditions.
LED Indicator Condition Meaning
OK Green Normal Operation
OK Off Power Disconnected or Battery Over-voltage
OK Red Low Supply voltage or Internal Module fault
Radio RX Green flash Radio receiving data
Radio RX Red flash Weak radio signal
Radio TX Flash Radio Transmitting
RS232 flash RS232 Serial Port Activity
RS485 flash RS485 Serial Port Activity
DCD Green Modem is Online and ready to send data.
DCD Red Modem is Online but Currently in Command Mode
DCD Off Communications failure or data connection not
established
Other conditions indicating a fault are described in Chapter Six Troubleshooting.
3.2 Serial and Radio Data
The 455U module provides a full-duplex RS232 serial port and half-duplex RS485 serial
port. The radio communications is half-duplex - this means that the 455U operates at half
duplex. Many applications use full duplex RS232 communications but do not require full
duplex - the protocol used operates at half-duplex and will operate with the 455U without
problems. If an application really requires full duplex communications, then the 455U should
not be used.
Data input at the serial port is placed into the input buffer. This buffer will store up to
8Kbytes of data, and CTS/RTS control can be configured on the RS232 port to prevent
overflow.