Pin sleep

Pin sleep allows the module to sleep and wake according to the state of the SLEEP_RQ pin (TH pin 9/SMT pin 10). Pin sleep mode is enabled by setting the SM command to 1.

When the device asserts (high) SLEEP_RQ, it finishes any transmit or receive operations for the current packet that is processing and enters a low power state. For example, if the device has not joined a network and SLEEP_RQ is asserted (high), it sleeps once the current join attempt completes (that is, when scanning for a valid network completes). The device wakes from pin sleep when the SLEEP_RQ pin is de-asserted (low). The following figures show the device's sleep pins.

Surface-mount sleep pins

Through-hole sleep pins

The following figure show the pin sleep waveforms:

In the previous figure, t1, t2, t3 and t4 represent the following events:

• t1 - Time when Sleep_RQ is asserted (high)
• t2 - Time when the device enters sleep (CTS state change only if hardware flow control is enabled)
• t3 - Time when Sleep_RQ is de-asserted (low) and the device wakes
• t4 - Time when the module sends a poll request to its parent

The time between t1 and t2 varies depending on the state of the module. In the worst case scenario, if the end device is trying to join a network, or if it is waiting for an acknowledgment from a data transmission, the delay could be up to a few seconds. The time between t3 and t4 is 1-2 ms for a regular device and about 6 ms for a PRO device.

When the XBee/XBee-PRO Zigbee RF Module is awake and is joined to a network, it sends a poll request to its parent to see if the parent has any buffered data. The end device continues to send poll requests every 100 ms while it is awake.

Demonstration of pin sleep

Parent and remote devices must be configured to buffer data correctly and to use adequate transmission timeouts. For more information, see Router/Coordinator configuration.