Digi XBee3 802.15.4 User Manual

Sleep support Sleep modes
Digi XBee3® 802.15.4 RF Module User Guide
76
Sleep modes
Sleep modes enable the device to enter states of low-power consumption when not in use. To enter
Sleep mode, the following conditions must be met:
n A valid sleep mode is selected via SM (SM = 1, 4, or 5)
n SLEEP_RQ/DTR (TH pin 9/SMT pin 10) is asserted (when SM = 1 or 5)
n The device is idle (no data transmission or reception) for the amount of time defined by ST
command (when SM = 4 or 5)
The following table shows the sleep mode configurations.
Sleep mode Description
SM 0 No sleep
SM 1 Pin sleep
SM 4
Cyclic sleep
SM5
Cyclic sleep with pin wake-up
Pin Sleep mode (SM = 1)
Pin Sleep mode minimizes quiescent power (power consumed when in a state of rest or inactivity). In
order to use Pin Sleep mode, configure D8 command (TH pin 9/SMT pin 10) for SLEEP_RQ input (D8 =
1). This mode is voltage level-activated; when SLEEP_RQ is asserted, the device finishes any transmit
or receive activities, enters Idle mode, and then enters a state of sleep. The device does not respond
to either serial or RF activity while in pin sleep.
To wake a sleeping device operating in Pin Sleep mode, de-assert SLEEP_RQ. The device wakes when
SLEEP_RQ is de-asserted and is ready to transmit or receive when the CTS line is low. When waking
the device, the pin must be de-asserted at least two 'byte times' after CTS goes low. This assures that
there is time for the data to enter the DI buffer.
Devices with SPI functionality can use the SPI_SSEL pin instead of D8 for pin sleep control. If D8 = 0
and P7 = 1, SPI_SSEL takes the place of SLEEP_RQ and functions as described above. In order to use
SPI_SSEL for sleep control while communicating on the UART, the other SPI pins must be disabled (P5,
P6, and P8 set to 0). See Low power operation for information on using SPI_SSEL for sleep control
while communicating over SPI.
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 XBee3 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.

Digi XBee3 802.15.4 Specifications

General

Brand	Digi
Model	XBee3 802.15.4
Category	Control Unit
Language	English