Serial interface specification: Detailed pin description
RIM 801D OEM Radio Modem – Integrator’s Guide
21
DSR
Data Set Ready is an output from the radio unit. This signal is electrically
connected to the DTR input and will therefore have the same properties as
the Host’s DTR output.
When the Radio unit is off, this line will be low from inside the radio
modem with an impedance of at least 20 k
Ω
.
RTS
Request To Send is an input to the Radio unit from the host. This line
should be asserted low by the host to indicate that data is waiting to be sent.
CTS
Clear To Send is an output from the Radio unit that indicates it is ready to
receive data from the Host. When this line is high any data sent from the
Host to the Radio may be lost.
This line will be low from inside the radio modem with an impedance of at
least 20 k
Ω
.
RI
Ring Indicator is an output from the Radio that can be used to wake up a
sleeping Host system. If the radio is flow controlled off (DTR or RTS
asserted high) and the Radio receives a packet, it will assert RI low to alert
the Host system that there is a data packet waiting.
This line is low when the radio is powered off, and has a source impedance
of 21 k
Ω
(when high) or 1 k
Ω
(when low).
TRI
Transmit Indicator is an output from the radio that is asserted high
whenever the Radio is transmitting a packet. This line can be used as
feedback to the host to ensure the radio is transmitting packets, or it can
