14.2.1.2.6 RX_ON_NOCLK - RX Listen State without CLKM

In RX_ON_NOCLK state the receiver is in the RX data polling mode with CLKM output disabled.

If the radio transceiver is listening for an incoming frame and the microcontroller is not running an application, the microcontroller may be powered down to decrease the total system power consumption. This specific power-down scenario – for systems running in clock synchronous mode – is supported by the AT86RF212B using the state RX_ON_NOCLK.

This state can only be entered by asserting pin 11 (SLP_TR) = H while the radio transceiver is in RX_ON state. Pin 17 (CLKM) is disabled 35 CLKM cycles after the rising edge at pin 11 (SLP_TR). This allows the microcontroller to complete its power-down sequence(1).

Once in RX_ON_NOCLK state a valid SHR header triggers a state transition to BUSY_RX state. The reception of a frame shall be indicated to the microcontroller by an interrupt indicating the receive status. CLKM is turned on again, and the radio transceiver enters the BUSY_RX state. When using RX_ON_NOCLK, it is essential to enable at least one interrupt request indicating the reception status.

After the receive transaction has been completed, the radio transceiver enters the RX_ON state. The radio transceiver only reenters the RX_ON_NOCLK state when the next rising edge of pin 11 (SLP_TR) occurs.

If the AT86RF212B is in the RX_ON_NOCLK state and pin 11 (SLP_TR) is reset to logic low, it enters the RX_ON state and it starts to supply clock on pin 17 (CLKM) again(2).

Note:
  1. For CLKM clock rates 250kHz and symbol clock rates (TRX_CTRL_0.CLKM_CTRL values six and seven), the master clock signal CLKM is switched off immediately after the rising edge of pin 11 (SLP_TR).
  2. A reset in state RX_ON_NOCLK further requires to reset pin 11 (SLP_TR) to logic low, otherwise the radio transceiver enters directly the SLEEP state.