Is SWCLK required for SWD ?

[JSchn.5]

The four wire interface from the ST-LINK V2 has no clock.

Where does it say that ST devices do not require a clock for SWD ?

Also why is it seemingly impossible to work through a hub ? This makes life very difficult.

[S.Ma]

SWD = Arm Serial Wire Debug.

Minimal wirering is monodir clock from debug probe to target chip, swdio is a bi directional signal. Ground is of course needed. In low power mode, sometime the core needs a reset pulse which the debug probe optionally provide.

[S.Ma]

ST link V2 4 pin connector is for STM8 SWIM single wire interface. Focus on the 20 pin connector.

[Andrew Neil]

Indeed, the 4-pin connector is marked "STM8", and the 20-pin is marked "STM32" on the unit itself, and this is CLEARLY documented in the User Manual:

 

 https://www.st.com/en/development-tools/st-link-v2.html#documentation