XBee-PRO XSC RF Module operation Operating modes
XBee®-PRO 900HP/XSC RF Modules
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Once in Pin Sleep, the device de-asserts (high) CTS (pin ) , indicating that other devices should not
send data to the device. The device also de-asserts (low) the TX_PWR line (pin ) when the device is in
Pin Sleep mode.
You cannot assert the SLEEP (pin9) until the transmission of the second byte has started.
Note The device completes a transmission or reception before activating Pin Sleep.
Cyclic Sleep Mode (SM = 4 - 8)
Cyclic Sleep modes allow device wakes according to the times designated by the cyclic sleep settings.
If the device detects a wake-up initializer during the time it is awake, the device synchronizes with the
transmitting device and receives data after the wake-up initializer runs its duration. Otherwise, the
device returns to Sleep mode and continues to cycle in and out of activity until a wake-up initializer is
detected.
While the device is in Cyclic Sleep mode, it de-asserts (high) CTS (pin ) to indicate not to send data to
the device. When the device awakens to listen for data, it asserts CTS and transmits any data received
on the DI pin. The device also de-asserts (low) the TX_PWR (pin ) when it is in Cyclic Sleep mode.
The device remains in Sleep mode for a user-defined period of time ranging from 1 second to 16
seconds (SM parameters 4 through 8). After this interval of time, the device returns to Idle mode and
listens for a valid data packet. The listen time depends on the BR parameter setting. The default BR
setting of 1 requires at least a 35 ms wake time, while the BR setting of 0 requires a wake time of up
to 225 ms. If the device does not detect valid data on any frequency, it returns to Sleep mode. If it
detects valid data, it transitions into Receive mode and receives the incoming RF packets. The device
then returns to Sleep mode after a period of inactivity determined by the ST parameter.
You can also configure the device to wake from cyclic sleep when the SLEEP pin is de-asserted. To
configure a device to operate in this manner, you must send the PW (Pin Wake-up) command. When
you de-assert the SLEEP pin, it forces the device into Idle mode and it can begin transmitting or
receiving data. It remains active until it no longer detects data for the time that ST specifies, at which
point it resumes its low-power cyclic state.
Cyclic scanning
Each RF transmission consists of an RF initializer and payload. The RF initializer contains initialization
information and all receiving devices must wake during the wake-up initializer portion of data
transmission in order to synchronize with the transmitting device and receive the data.
The cyclic interval time defined by the SM (Sleep Mode) command must be shorter than the interval
time defined by LH (Wake-up Initializer Timer) command.
Correct configuration (LH > SM)
In the following figure, the length of the wake-up initializer exceeds the time interval of Cyclic Sleep.
The receiver is guaranteed to detect the wake-up initializer and receive the accompanying payload
data.
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