Synthesised Radio Modem
2.2
LED Indicators
Three LEDS on the front of the modem indicate the following states:
TX
Green
RX
Green
POWER Red
X8200
X8200HP
On when modem is transmitting data.
On when a RF carrier of greater than 0.9uV is detected by the modem.
On when power is applied to the modem
2.3
Antenna Connector
BNC/TNC
3
Operation
A transmission is started by sending data to RD (pin 2) or the RS485 terminals (pin7 & 9).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. When Tx Priority is set, data will be transmitted regardless of
the condition of the RF Channel.
The modem will then transmit a command byte which will instruct the distant modems to perform the functions set in
the menu followed by the addressing and repeater functions. The data that has been placed in the buffer memory will
then be transmitted. 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 packetisation option is selected the receiving modem will check the CRC byte. If it is correct an ACK sent to the
transmitting modem. If the CRC is incorrect a NACK is sent to the transmitting modem and the data is sent again.
The number of re-trys are set in the Menu.
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.
4
4.1
Getting started
Basic Connection
TRANSMIT
RECEIVE
GROUND
(TD)
(RD)
(0V)
ON HOST TO RECEIVE (RD) ON MODEM PIN 2
ON HOST TO TRANSMIT (TD) ON MODEM PIN 3
ON HOST TO 0V ON MODEM PIN 5
4.2
Power Connection
PIN 1 = POSITIVE
PIN 5 = GND
DS8200-2 April ’07
©2007 RF Solutions Ltd, www.rfsolutions.co.uk
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