Sleep/ Deep sleep state

Hi , I am facing issue to understand the mode my STM32WB55RG gets into when mbed invokes sleep function .
I am making use of following function to get MCU into sleep :


Can someone enlighten me how mbed configures various modes ? Am I right in assuming mbed makes use of HAL libraries provided by STMicro for various power saving modes?

Basically , I want to know in which mode my controller gets into and how these functions are cascaded?
I want my MCU to be consuming as low current as possible.

Any help and resources will be greatly appreciated.

Thanks in advance.

Have a look here:

Should give you some ideas.
Most ST’s operate the same way.
More info here too: