XBee‐PRO®900HP/XBee‐PRO®XSCRFModules
©2014DigiInternationalInc. 28
XBee-PRO 900HP Serial Interface Protocols
The XBee modules support both transparent and API (Application Programming Interface) serial interfaces.
Transparent Operation - UART
When operating in transparent mode, the modules act as a serial line replacement. All UART data received
through the DIN pin is queued up for RF transmission. When RF data is received, the data is sent out
through the serial port. The module configuration parameters are configured using the AT command mode
interface. Please note that transparent operation is not provided when using the SPI.
Data is buffered in the serial receive buffer until one of the following causes the data to be packetized and
transmitted:
•No serial characters are received for the amount of time determined by the RO (Packetization Time-
out) parameter. If RO = 0, packetization begins when a character is received.
•The Command Mode Sequence (GT + CC + GT) is received. Any character buffered in the serial
receive buffer before the sequence is transmitted.
•The maximum number of characters that will fit in an RF packet is received. See the NP parameter.
API Operation
API operation is an alternative to transparent operation. The frame-based API extends the level to which a
host application can interact with the networking capabilities of the module. When in API mode, all data
entering and leaving the module is contained in frames that define operations or events within the module.
Transmit Data Frames (received through the serial port) include:
•RF Transmit Data Frame
•Command Frame (equivalent to AT commands)
Receive Data Frames (sent out the serial port) include:
•RF-received data frame
•Command response
•Event notifications such as reset, etc.
The API provides alternative means of configuring modules and routing data at the host application layer. A
host application can send data frames to the module that contain address and payload information instead
of using command mode to modify addresses. The module will send data frames to the application
containing status packets; as well as source, and payload information from received data packets.
The API operation option facilitates many operations such as the examples cited below:
-> Transmitting data to multiple destinations without entering Command Mode
-> Receive success/failure status of each transmitted RF packet
-> Identify the source address of each received packet
A Comparison of Transparent and API Operation
The following table compares the advantages of transparent and API modes of operation:
Transparent Operation Features
Simple Interface All received serial data is transmitted unless the module is in command mode.
Easy to support It is easier for an application to support transparent operation and command mode
API Operation Features
Easy to manage data
transmissions to multiple
destinations
Transmitting RF data to multiple remotes only requires changing the address in the API frame. This
process is much faster than in transparent operation where the application must enter AT command
mode, change the address, exit command mode, and then transmit data.
Each API transmission can return a transmit status frame indicating the success or reason for
failure.
Received data frames
indicate the sender's
address
All received RF data API frames indicate the source address.
Advanced addressing
support
API transmit and receive frames can expose addressing fields including source and destination
endpoints, cluster ID and profile ID.
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