Cyclic Sleep mode (SM = 4)

The Cyclic Sleep modes allow devices to periodically check for RF data. When the SM parameter is set to 4, the XBee 3 802.15.4 RF Module is configured to sleep, then wakes once per cycle to check for data from a coordinator. The Cyclic Sleep Remote sends a poll request to the coordinator at a specific interval set by the SP (Cyclic Sleep Period) parameter. The coordinator transmits any queued data addressed to that specific remote upon receiving the poll request.

If the coordinator does not respond with queued data and no UART activity is detected, the device will immediately sleep. If it detects any activity (RF or UART), then the device wakes for ST time. You can also set SO bit 8 to force the device to always wake for the full ST time.

ON_SLEEP goes high and CTS goes low each time the remote wakes, allowing for communication initiated by the remote host if desired.