User Interface
5
1
9
Figure 2: DB9F RS232 connector pin arrangement
Pin description
Pin
1
2
3
4
Name
I/O
out
out
in
in
-
Function
RX_FLOW
RX_DATA
TX_DATA
RX_HOLD
0V
RS232 'DCD' output. Active (+ve level) when data is present in rx buffer
RS232 'RXD' data out
RS232 'TXD' data in
RS232 'DTR' input. Take -ve to interrupt rx data output
Ground
5
6
7
ENABLE
N/C
in
-
RS232 'DSR' Pull low to enable unit. (Internal 20K pullup to Vraw)
(RTS pin on standard RS232)
8
9
TX_FLOW
+5V out
out
out
RS232 'CTS' output. Active (+ve level) when the tx buffer is nearly full
Regulated supply output. 500mA max. (switched by pin 6)
Jumpers
LK 1. link to hold unit permanently on (disables pin 6 switching)
LK 2. link to enable rx dataflow inhibit (DTR) input.
As supplied, all links are open
Power
This is a 2.1mm power connector. Center pin is positive.
Supply requirements are: 6-15v normal operation
NOTES:
1. All Input pins will tolerate true +/- RS232 levels. No buffering is required.
2. The modem provides a half duplex link: Provided no two devices attempt to transmit at one time (a
'high' on RX_FLOW may be used as a primitive 'other user on channel' indication) no further
restrictions on data transmission need be made, as all transmit timing, valid data identification and
datastream buffering is conducted by the unit. There is no 'transmit enable' pin. Sync and framing
words in the packet prevent the receiver outputting garbage in the absence of signal or presence of
interference
3. If the user interface rate has been set to greater than 4800 baud, then the modem cannot empty the
128 byte tx data buffer as quickly as the user can fill it. In this case it is either necessary to limit the
average data throughput, or to monitor the TX_FLOW (CTS) output, and interrupt the dataflow when
this pin signals a full buffer.
TX_FLOW activates when the buffer is 3/4 full, and deactivates when it is empty
4. A fairly complex addressing structure is included in the datastream. Units have four independent
(OR'ed) receive addresses and a separate transmit address. (all units are supplied set to tx address
=1, rx addr1 = 0, rx addr2-4 = 1)
Note: For details relating to the radio module fitted on board, see FPX3 datasheet
http://www.radiometrix.com/files/additional/FPX3.pdf
Radiometrix Ltd, M48A-869-FPX3 modem manual
page 2
RADIOMETRIX [ RADIOMETRIX LTD ]
