User manual

905U-D Radio Modem User Manual
Man_905D_1.10.doc Page 18
Chapter Three OPERATION
3.1 Power-up and Normal Operation
When power is initially connected to the 905U-D 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
On
Normal Operation
Radio RX GREEN flash
RED flash
Radio receiving data
Weak radio signal
Radio TX
Flash
Radio Transmitting
Serial RX
GREEN flash
RED flash
Serial Port Receiving
CTS low
Serial TX
GREEN flash
Serial Port Transmitting
DCD On Transparent mode - always on
Controlled mode - on when
communications link is established
DCD
Off
Communications failure or link not
established
Other conditions indicating a fault are described in Chapter Six Troubleshooting.
3.2 Serial and Radio Data
The 905U-D module provides a full-duplex RS232 serial port and half-duplex RS485 serial port
- only one serial port can be used at any one time. The radio communications is half-duplex -
this means that the 905U-D 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 905U-D without problems. If an application really requires full duplex
communications, then the 905U-D should not be used.
Data input at the serial port is placed into the input buffer. This buffer will store 2Kbytes of
data, and CTS/RTS control can be configured on the RS232 port to prevent overflow.