14.1.6.2 RX_ON and RX_AACK_ON States

For synchronous systems where CLKM is used as a microcontroller clock source and the SPI master clock (SCLK) is directly derived from CLKM, the AT86RF212B supports an additional power-down mode for receive operating states (RX_ON and RX_AACK_ON).

If an incoming frame is expected and no other applications are running on the microcontroller, it can be powered down without missing incoming frames. This can be achieved by a rising edge on pin 11 (SLP_TR) that turns CLKM off. Then the radio transceiver state changes from RX_ON or RX_AACK_ON (Extended Operating Mode) to RX_ON_NOCLK or RX_AACK_ON_NOCLK, respectively. In case that a frame is received (for example indicated by an IRQ_2 (RX_START) interrupt), the clock output CLKM is automatically switched on again. This scenario is shown in the figure below. In RX_ON state, the clock at pin 17 (CLKM) is switched off after 35 CLKM cycles when setting SLP_TR = H.

The CLKM clock frequency settings for CLKM_CTRL values six and seven are not intended to directly clock the microcontroller. When using these clock rates, CLKM is turned off immediately when entering RX_ON_NOCLK or RX_AACK_ON_NOCLK.

In states RX_(AACK)_ON_NOCLK and RX_(AACK)_ON, the radio transceiver current consumptions are equivalent. However, the RX_(AACK)_ON_NOCLK current consumption is reduced by the current required for driving pin 17 (CLKM).