Cesar Manzanarez Ayala

KW0x clocking considerations to send the xcvr to Sleep and Listen (Idle + Rx) mode

Discussion created by Cesar Manzanarez Ayala Employee on Oct 3, 2014
Latest reply on Oct 7, 2015 by Luis Antonio Burgos Lopez
Branched to a new discussion

In a power sensitive application sending both the xcvr and the MCU to a low power mode is necesssary.

Sleep and Idle modes are the lowest consumption modes that can be achieved in the xcvr, with 0.1 uA and 1.2 uA respectively (For

more details refer to the device datasheet)


It's a common practice to feed the xcvr with an external clock and use the CLKOUT signal provided by the xcvr to feed the

MCU. In this scenario considerations need to be taken prior to sending the xcvr to any of the above power modes because the

CLKOUT signal is not available in any of these modes.



*Sleep Mode*


1) Change the MCU to a clocking mode that doesn't feed from the external CLKOUT signal


Change to an internal clock source like FEI (FLL Engaged Internal)


2) Set Sequencer Off

This is achieved by writting to the corresponding xcvr register: RegOpmode (0x01)

Set bit SequencerOff to 1.


This allows to go direclty to the selected operating mode (Sleep or Idle).


3) Set the desired Operation mode

This is achieved by writting to the corresponding xcvr register: RegOpmode (0x01)

Write bits MODE (4-2) to send the xcvr to the desired mode.

Sleep= 000


*Listen Mode*

Prior to following steps 1-3 the user will need to configure registers RegListen1, RegListen2, RegListen3

to indicate Idle times and RX times.


Step 0)

- Configure RegListen1


RegListen1(0x0D)= 0xD0 -> This will configure Idle time resolution to 262ms (MAX) and Rx time resolution to 64uS (MIN)

- Configure RegListen2


RegListen2(0x0E)= 0xFF -> This will set the duration of the Idle phase to 255. TOTAL IDLE PHASE TIIME  = 255 * 262mS= 66.81 Seconds

- Configure RegListen3


RegListen3(0x0F)= 0x01 -> This will set the duration of the Rx phase to 1. TOTAL RX PHASE TIIME    = 1 * 64uS= 64 uS


After this you can follow steps 1-3 indicated in Sleep Mode.

*Note: In step 3 set the MODE (4-2) bits to "StandBy"

StandBy= 001