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RF Module operation
Serial communications
The XBee ZNet 2.5 OEM RF Modules interface to a host device through a logic-level asynchronous
serial port. Through its serial port, the module can communicate with any logic and voltage
compatible UART; or through a level translator to any serial device; for example: through a Digi
proprietary RS-232 or USB interface board.
UART data flow
Devices that have a UART interface can connect directly to the pins of the RF module as shown in the
figure below.
Figure 5: System data flow diagram in a UART-interfaced environment. Low-asserted signals are
distinguished with horizontal line over signal name.
Serial data
Data enters the module UART through the DIN (pin 3) as an asynchronous serial signal. The signal
should idle high when no data is being transmitted.
Each data byte consists of a start bit (low), 8 data bits (least significant bit first) and a stop bit (high).
The following figure illustrates the serial bit pattern of data passing through the module.
The module UART performs tasks, such as timing and parity checking, that are needed for data
communications. Serial communications depend on the two UARTs to be configured with compatible
settings (baud rate, parity, start bits, stop bits, data bits).
Serial buffers
The XBee ZNet 2.5 modules maintain small buffers to collect received serial and RF data, which is
illustrated in the figure below. The serial receive buffer collects incoming serial characters and holds
XBee ZNet 2.5 / XBee PRO Znet 2.5 OEM RF Modules Product Manual
Serial communications
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