2.3 HOST
TO RADIO PACKET MODE DATA TRANSFER
Data is transferred between the RPM1 and the HOST using an asynchronous serial protocol. The default
protocol settings are 8 data bits, no parity and 1 stop bit (8n1). The baud rate setting for the serial
interface is user settable from 600bps to 115200bps.
TXD
Data from the connected host (DTE) is received by the RPM1 through TXD pin.
CTS
A single handshake line, CTS, controls the flow of data into the RPM1. The serial receive buffer of
the RPM1 is 96 bytes deep. The CTS will be asserted High (VCC) by the RPM1 when the receive
buffer hits approximately 66% full. It is advisable to limit the number of characters sent to the
RPM1 after the CTS control line is asserted. This will help to reduce the possibility of lost data
due to internal buffer overruns in the RPM1. The RPM1 will clear the CTS when the internal
serial receive buffer falls below 33% full.
RXD
Upon the RPM1 receiving data from a remote unit, the received data is sent to the connected host
(DTE) device through the RXD pin.
2.4 ENTERING
RADIO PACKET MODEM CONFIGURATOR
Configuring the RPM1 is accomplished by using a built-in command line configurator. The configurator
is entered by asserting the SETUP input of the RPM1 while resetting the RPM1.
S
ETUP
Holding SETUP low during a reset cycle will force the modem into the configurator. The state of
this input is checked while the RPM1 starts up from either power on or reset.
HOST DRIVEN SETUP
The Setup pin may either be driven by the host (recommended) to enable host controlled
configuration of the RPM1 or pulled up to VCC via a suitable pull-up resistor (10kΩ).
2.5 FORCING
DEFAULT SERIAL BAUD RATE
Asserting this pin low forces the RPM1 to start-up with a default baud rate of 9600bps, 8 data bits, one
stop and no parity.
DEFAULT
During a RESET the HOST must hold DEFAULT low to force the RPM1 serial interface to default to
9600bps. This is ideal if the serial baud rate has been forgotten or incorrectly set.
HOST DRIVEN DEFAULT
The DEFAULT pin may either be driven by the host (recommended) or pulled up to VCC via a
suitable pull-up resistor (10kΩ).
2.6 FORCING
RADIO PACKET MODEM INTO SLEEP MODE
Asserting the WAKE input high forces the modem into a low power sleep mode. This effectively shuts
down the RPM1 and prevents it from sending or receiving any data. It is a method for conserving power
when the modem is not required.
WAKE / DTR
During normal operation WAKE pin can be pulled high to force the RPM1 to shutdown into low
power sleep mode.
HOST DRIVEN WAKE
The WAKE pin may either be driven by the host (recommended) or pulled Low to 0V.
Radiometrix Ltd.
VHF Narrow Band FM Radio Packet Modem
page 5
RADIOMETRIX [ RADIOMETRIX LTD ]
