RPM3-914-17-RPS datasheet(5/15 Pages) RADIOMETRIX

5 / 15 page

Radiometrix Ltd.

UHF FM Radio Packet Modem

page 5

2.3 HOST TO RADIO PACKET MODE DATA TRANSFER

Data is transferred between the RPM3 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 RPM3 through TXD pin.

CTS

A single handshake line, CTS, controls the flow of data into the RPM3. The serial receive buffer of

the RPM3 is 96 bytes deep. The CTS will be asserted High (VCC) by the RPM3 when the receive

buffer hits approximately 66% full. It is advisable to limit the number of characters sent to the

RPM3 after the CTS control line is asserted. This will help to reduce the possibility of lost data

due to internal buffer overruns in the RPM3. The RPM3 will clear the CTS when the internal

serial receive buffer falls below 33% full.

RXD

Upon the RPM3 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 RPM3 is accomplished by using a built-in command line configurator. The configurator

is entered by asserting the SETUP input of the RPM3 while resetting the RPM3.

SETUP

Holding SETUP low during a reset cycle will force the modem into the configurator. The state of

this input is checked while the RPM3 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 RPM3 or pulled up to VCC via a suitable pull-up resistor (10k

Ω).

2.5 FORCING DEFAULT SERIAL BAUD RATE

Asserting this pin low forces the RPM3 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 RPM3 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 (10k

Ω).

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 RPM3 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 RPM3 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.

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