XBee-PRO XSC RF Module operation Operating modes
XBee®-PRO 900HP/XSC RF Modules
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n Command mode (Command mode sequence issued, not available with Smart Energy software
or when using the SPI port).
Transmit mode
When the device received the first byte of serial data from the UART in the DI buffer, the modem
attempts to shift to Transmit Mode and initiate an RF connection with other modems. After
completing the transmission, the modem returns to Idle Mode.
RF transmission begins after meeting either of the following criteria:
1. RB bytes have been received in the DI buffer and are pending for RF transmission. For more
information, see RB (Packetization Threshold).
The RB parameter may be set to any value between 1 and the RF packet size (PK), inclusive.
When RB = 0, the packetization threshold is ignored.
2. At least one character has been received in the DI buffer (pending for RF transmission) and RO
time has been observed on the UART. Refer to RO (Packetization Timeout).
- The time out can be disabled by setting RO to zero. In this case, transmission will begin after
RB bytes have been received in the DI buffer.
Note RF reception must complete before the modem is able to enter into Transmit Mode.
After meeting either RB or RO conditions, the modem initializes a communications channel. Channel
initialization is the process of sending an RF initializer that synchronizes receiving modems with the
transmitting modem. During channel initialization, incoming serial data accumulates in the DI buffer.
The device then:
n Groups serial data in the DI buffer (for more information, see PK (Maximum RF Packet Size)
n Converts the data to RF data
n Transmits the data over-the-air until the DI buffer is empty
RF data, which includes the payload data, follows the RF initializer. The payload includes up to the
maximum packet size (PK Command) bytes. As the transmitting modem nears the end of the
transmission, it inspects the DI buffer to see if more data exists to be transmitted. This could be the
case if more than PK bytes were originally pending in the DI buffer or if more bytes arrived from the
UART after the transmission began. If more data is pending, the transmitting modem assembles a
subsequent packet for transmission.
Receive mode
If a destination node receives a valid RF packet, the destination node transfers the data to its serial
transmit buffer. For the serial interface to report receive data on the RF network, that data must
meet the following criteria:
n ID match
n Channel match
n Address match
Sleep mode
Sleep Modes enable the device to operate at minimal power consumption when not in use. The
following Sleep mode options are available:
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