How to let LSM6DSOX enter I3C mode

[Abner]

Product https://www.st.com/en/mems-and-sensors/lsm6dsox.html

About the below datasheet description, I want to confirm exact I2C Fast mode Plus timing. Should this SETDASA/ENTDAA follow all timing parameters as I2C Fm+? For NXP I3C, it’s not hard to set a suitable baud rate for this, but it’s impossible to meet all timing for a ENTDAA operation. Can ST I3C IP run ENTDAA with I2C timing to meet your sensor product?
 

 

[Federica Bossi]

Hi ​@Abner ,

Yes, for LSM6DSOX, the address assignment (DAA or ENTDAA) must be performed with I²C Fast Mode Plus timing. Once the slave is addressed, the I²C slave is disabled and the timing becomes compatible with I3C specifications

[Abner]

Hi Federica,

OK. So design expectation is the bus controller needs to operate I²C Fast Mode Plus timing to finish ENTDAA.
But ENTDAA itself is a kind of I3C operation. How to make I3C operation timing to meet I²C Fast Mode Plus timing.
Is ST I3C IP can do this? How to let other vendor to use your sensor without this timing feature? I doubt this I²C Fast Mode Plus timing is just baud rate speed instead of full timing parameters such as tSU:STO。

[Abner]

​@Federica Bossi Any update of this? The details is not clear in datasheet. We can only guess the mechanism but not confirm.

[Federica Bossi]

Hi ​@Abner ,

When I²C/I3C coexistence is used, the address assignment phase (ENTDAA or SETDASA) must be performed with I²C Fast Mode Plus timing.

This requirement is not limited to SCL frequency only: the datasheet also specifies the I²C Fast Mode Plus timing parameters, including SCL low/high times and START/STOP-related timing limits.

After the dynamic address is assigned, the I²C slave is disabled and the interface timing becomes compatible with I3C operation.

So, from the sensor side, there is no alternative mechanism to relax ENTDAA timing: the bus controller must be able to meet the Fast Mode Plus requirements during the address-assignment phase. If this cannot be guaranteed, the practical solution is to use only the I3C mode with the proper power-up configuration, or a static-address-based setup where applicable.