Radiometrix Ltd
TR2M Data Sheet
page 8
Pin description of TR2M with Modem mode selected
The 'modem' mentioned is a 1200 baud RS232 semi-intelligent unit (Transmit keyed when valid serial data is
present, so no separate TX control needed. Coding in the datastream also permits the receiver to ignore noise
and only output valid serial data). This is a half duplex unit, so collisions between transmitted and received
packets must be dealt with by the user.
Pin
Name
Function
1
MOD TX_ON
Open = normal modem operation. Low = constant TX (for test). 10k pullup to 4V
2
MOD NC
Leave open
3
MOD NC
Leave open
4
RSSI
DC level between 0.5V and 2.5V. 60dB dynamic range
5
MOD NC
Leave open
6
AF out
Modem tones or noise present
7
NC
Leave open
8
+4.4V out
Regulated DC supply. 75mA max. drain. Present if unit is powered
9
0V
Ground
10
PGM
Serial programming/configuration input at RS232 level
11
MOD TXD
RS232 data input (true). 10k pullup to 4V
12
MOD RXD
Inverted RS232 data out (to inverting buffer like MAX232)
13
MOD NC
Leave open
TR2Ms on both ends should be configured to required operating frequency using GOCHAN
command before starting to use the internal 1200 baud modem, because the P1-P3 pins will be used
as Modem Data pins and the modem will operate on the last serially selected channel after
SETMOD command is used to enable the Modem.
TXE (MOD TX_ON) (C1)
TXD (MOD NC) (C2)
AF in (MOD NC) (C3)
RSSI (C4)
SQF (MOD NC) (C5)
AF out (C6)
RXD (MOD NC) (C7)
+4.4V out (C8)
GND (C9)
PGM (C10)
P1 (MOD TXD) (C11)
P2 (MOD RXD) (C12)
P3 (MOD NC) (13)
1
2
3
TXD
RXD
SGD
4
6
7
8
9
5
Serial COM Port
RS232 driver
VDD
SW1
Figure 7: TR2M interfaced to PC serial port in modem mode
Note:
Baud rate used for Modem is half that of used for serial configuration. Attached RS232 devices
should be set with the following:
1200bps, 8 Data bits, No Parity, 1/2 stop bits, no flow control
TXD (Pin 3) of a Serial Port can be switched from PGM (Pin C10) to MOD TXD (Pin C11) with no
RS232 driver in between. However, MOD RXD (Pin C12) requires an RS232 line driver before it
can be connected to RXD (pin 2) of a serial port. Some of the RS232 line drivers can be powered
from the regulated +4.4V out (Pin C8).
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