User's Manual

Interface specification: Pin descriptions 41
RIM 902M OEM Radio Modem – Integrator’s Guide
Pin 19 ~DTR ~Data Terminal Ready
This line is an input to the radio.
The active (data terminal ready) state of this line is low, and indicates that the
computing device is ready to receive data from the RIM 900. De-asserting this
line high will turn communication off; the RIM 900 would not attempt to
deliver data to the computing device until ~DTR is again asserted low.
Asserting this line low will cause the radio to send a MASC B frame to the
computing device if MASC is the protocol being used, and will allow
communication to resume.
If you do not intend to use ~DTR, tie it to ground to ensure that it is always
asserted during radio operation.
This line should be driven low when the radio is off. Driving ~DTR high when
the radio is off will consume unnecessary power.
Pin 20 TX Transmit
This line is an input to the radio. Its idle (no data) state is high.
This is an asynchronous serial input to the radio unit, and should be connected
to the computing device’s Transmit Data output. This line carries data at 9600
bits per second. MASC parameters are 7 bits, Even parity, 1 stop bit. RAP
parameters are 8 bits, No parity, 1 stop bit.