Which should be connected to ST-LINK, VDD(3.3V) or VDDIO(2.8V)?

[ayasu.1]

Hello 

I am designing a circuit with STM32F098RCTx. 

I'd like to know about the operation when VDD = 3.3V and VDDIO = 2.8V.

SWD uses PA13 (SWDIO) and PA14 (SWCLK). 

The datasheet says:

"PC6, PC7, PC8, PC9, PA8, PA9, PA10, PA11, PA12, PA13, PF6, PA14, PA15, 

 PC10, PC11, PC12, PD0, PD1 and PD2 I / Os are supplied by VDDIO2" 

Therefore, SWDIO and SWCLK are considered to operate at 2.8V.

When using ST-LINK , you need to connect VDD, GND, SWDIO, SWCLK, RESET Pin.

The problem here is the power supply to ST-LINK. 

The RESET pin should operate at VDD (3.3V). 

Is it better to connect ST-LINK to VDD (3.3V) or to VDDIO (2.8V)?

I think I should connect it to VDD (3.3V). What do you think?

thank you.

[Tesla DeLorean]

Either would be fine, the pins are tolerant, and the NRST is open-drain with a pull-up. Only the official ST-LINK/V2 buffers via VTarget pin

I'd probably use the 2.8V

[ayasu.1]

I understand.

Connect 2.8V to VDD of ST-LINK.

I got it. Thank you for your response!