I3C TARGET : How to detect when the controller requests data ?

[MedFedi]

Hello,
I'm currently working with I3C in Target mode using STM32H7S3L8. I need to detect when the Controller sends a request to read data from the Target.
In I2C, we can check the Address Match (ADDR) flag to know when the master sends a frame to the slave.
Is there a similar flag or event in I3C to detect when the Controller is requesting data from the Target (i.e., a read request)?
I'm using the I3C HAL/LL drivers, and I want to handle this case to prepare and send the correct response.
Thanks in advance!

[JRAUL.1]

Hello,

And good point. On I2C, it was possible to use an information of direction through a specific callback named

HAL_I2C_AddrCallback.

At I2C driver level, it works as the Stretch mode is used and so it was possible to "delay" the Master/slave communication until Slave was ready to receive or transmit data.

On I3C level, link to MIPI specification the stretch mode is forbidden. So it is not possible to delay a started private communication. So not possible to have a delay to inform application that a private transmit or receive communication is requested.

The best way to perform an unknown communication direction, is:
To manage a protocol on application side like:
Controller send a first specific transmit with a Code which can be detected like a transmit or receive at next communication.
And then at Target side, thx to this received code, the target will be able to prepare the private communication to a transmit or a receive.

This start of communication by using function 

HAL_I3C_Tgt_Transmit_IT or HAL_I3C_Tgt_Receive_IT can be called inside the HAL_I3C_TgtRxCpltCallback.

Hope it helps, MIPI I3C add some private communication restriction in comparison of I2C as no stretch is possible.
Regards

[MedFedi]

Hello,
Thanks Jerome for replying,
In I3C, we can use the RXFNEF flag to check for data reception in the target (to read incoming data).
I would like to know which flag I can use in the target to detect when the controller is requesting data, meaning the target must transmit data to the controller.
Thank you in advance.

[JRAUL.1]

If you want to manage Target transmit communication at flag level, without using HAL, for Target you can check the flag TXFNFF into I3C_EVR register.

For more details, please check the reference manual of the product a section "TX-FIFO management, as target"

Thx and Regards