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 (DIO8/DTR/SLP_Request Configuration) (TH pin 9/SMT pin 10) for DTR/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 DTR/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 DTR/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.