Sleep modes
Asynchronous cyclic sleep mode
XBee 868LP RF Modules User Guide
85
Pin sleep allows the device to sleep and wake according to the state of the SLEEP_RQ pin (pin 10).
When you assert SLEEP_RQ (high), the device finishes any transmit or receive operations and enters a
low-power state.
When you de-assert SLEEP_RQ (low), the device wakes from pin sleep.
Asynchronous cyclic sleep mode
Set
SM
to 4 to enter asynchronous cyclic sleep mode.
Cyclic sleep allows the device to sleep for a specific time and wake for a short time to poll.
If the device receives serial or RF data while awake, it extends the time before it returns to sleep by
the specific amount the
ST
command provides. Otherwise, it enters sleep mode immediately.
The ON_SLEEP line asserts (high) when the device wakes, and is de-asserted (low) when the device
sleeps.
If you use the
D7
command to enable hardware flow control, the CTS pin asserts (low) when the
device wakes and can receive serial data, and de-asserts (high) when the device sleeps.
Asynchronous cyclic sleep with pin wake up mode
Set
SM
to 5 to enter Asynchronous cyclic sleep with pin wake up mode.
This mode is a slight variation on (
SM
= 4) that allows the device to wake prematurely by asserting the
SLEEP_RQ pin (pin 9). In (
SM
=5 ), the device wakes after the sleep period expires, or if a high-to-low
transition occurs on the SLEEP_RQ pin.
Synchronous sleep support mode
Set
SM
to 7 to enter synchronous sleep support mode.
A device in synchronous sleep support mode synchronizes itself with a sleeping network but will not
itself sleep. At any time, the device responds to new devices that are attempting to join the sleeping
network with a sync message. A sleep support device only transmits normal data when the other
devices in the sleeping network are awake. You can use sleep support devices as preferred sleep
coordinator devices and as aids in adding new devices to a sleeping network.
Synchronous cyclic sleep mode
Set
SM
to 8 to enter synchronous cyclic sleep mode.
A device in synchronous cyclic sleep mode sleeps for a programmed time, wakes in unison with other
nodes, exchanges data and sync messages, and then returns to sleep. While asleep, it cannot receive
RF messages or receive data (including commands) from the UART port.
Generally, the network’s sleep coordinator specifies the sleep and wake times based on its
SP
and
ST
settings. The device only uses these parameters at startup until the device synchronizes with the
network.
When a device has synchronized with the network, you can query its sleep and wake times with the
OS
and
OW
commands respectively.
If
D9
= 1 (ON_SLEEP enabled) on a cyclic sleep node, the ON_SLEEP line asserts when the device is
awake and de-asserts when the device is asleep.
If
D7
= 1, the device de-asserts CTS while asleep.
