SN32F280 Series
32-Bit Cortex-M0 Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 254
Version 1.1
22.4.3 INTERNAL PULL-UP/DOWN RESISTORS on SWD PINS
To avoid any uncontrolled IO levels, the device embeds internal pull-up and pull-down resistor on the SWD input pins:
NJTRST: Internal pull-up
SWDIO/JTMS: Internal pull-up
SWCLK/JTCK: Internal pull-down
Once a SWD function is disabled by SW, the GPIO controller takes control again.