3.1.2 9 Way D Type Connector RS485
1
+12V
INPUT
6
CONFIGURATION
MODE
INPUT
2
DATA IN
RS485 IN
INPUT
7
DATA IN
RS485 IN
INPUT
3
DATA
OUT
RS485
OUT
OUTPUT
8
DATA
OUT
RS485
OUT
OUTPUT
4
DTR
(STANDBY)
INPUT
9
CD
CARRIER
DETECT
OUTPUT
5
0v
INPUT
3.2 LED
Indicators
Three LEDS on the front of the modem indicate the following states:
TX
Green
On when modem is transmitting data.
RX
Green
On when a RF carrier of greater than 0.9uV is detected by the modem.
This threshold can be adjusted by a potentiometer inside the modem.
POWER Red
On when power is applied to the modem
4.0 OPERATION
A transmission is started by sending data to RD (pin 2) on the serial port. The radio modem
places this data in the transmitter buffer memory while it checks to see if the RF. channel is
free. If it is not then the data is stored in the buffer until the channel becomes free. If it is free
then a preamble message will be transmitted so that the receiving modems can align to the
incoming data.
The modem will then transmit a repeater command byte, if set, and a transmitter address
byte followed by the data that has been placed in the buffer memory. The transmission is
terminated when a gap of two data bytes is detected in the incoming data stream.
If more data is sent after a gap of two data bytes then the above sequence will be repeated.
When the receiving modem detects the presence of incoming data it takes CTS (pin 8) low.
The repeater command byte is decoded and the transmitter address compared to the
receiver address. If they are the same or if the global address of 00 is decoded or if the
address mode is switched off then the data will be presented at the serial output port TD (pin
3). At the end of the message CTS is taken high.
If the repeater command is decoded or the repeater mode set in the configuration menu then
the data will be stored and then re-transmitted.
The best results are obtained from the radio modem by setting the transmission speed to the
slow setting and the baud rate to either 4800 or 9600.
5.0 GETTING
STARTED
5.1 Basic
Connection
TRANSMIT
(TD) ON HOST TO RECEIVE (RD) ON MODEM PIN 2
RECEIVE
(RD)
ON HOST TO TRANSMIT (TD) ON MODEM PIN 3
GROUND
(0V)
ON HOST TO 0V ON MODEM PIN 5
