Accessing A111 registers via the SPI interface is not supported. The main reason is that to make changes to the registers, one must have knowledge about proprietary design details which are confidential. The performance of the sensor also depends on nontrivial calibration and signal processing software that is included in the software libraries.
The sensor is controlled using the Software API “Radar Services” and all settings are done using this API. A description of how to change the settings as well as a description of the radar data provided by the different services is documented in the user guides that are available on the Acconeer webpage.