Product Manual

©2007MaxStream,Inc. 9
2.RFModuleOperation
2.1. Serial Communications
The XBee/XBee-PRO OEM RF Modules interface to a host device through a logic-level asynchro-
nous 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 Max-
Stream proprietary RS-232 or USB interface board).
2.1.1. 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2‐01. SystemDataFlowDiagraminaUART‐interfacedenvironment
(Low‐assertedsignalsdistinguishedwithhorizontallineoversignalname.)
Serial Data
Data enters the module UART through the DI pin (pin 3) as an asynchronous serial signal. The sig-
nal 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.
Figure2‐02. UARTdatapacket0x1F(decimalnumberʺ31ʺ)astransmittedthroughtheRFmodule
ExampleDataFormatis8‐N‐1(bits‐parity‐#ofstopbits)
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 compati-
ble settings (baud rate, parity, start bits, stop bits, data bits).