Swd Pin Assignment; Internal Pull-Up And Pull-Down On Swd Pins; Swd Port Connection With Standard Swd Connector - ST STM32F0 Series Application Note

Debug management
5.3.2

SWD pin assignment

After reset (SYSRESETn or PORESETn), the pins used for the SWD are assigned as
dedicated pins which are immediately usable by the debugger host.
However, the MCU offers the possibility to disable the SWD, therefore releasing the
associated pins for general-purpose I/O (GPIO) usage. For more details on how to disable
SWD port, refer to the RM0091 section on I/O pin alternate function multiplexer and
mapping.
5.3.3

Internal pull-up and pull-down on SWD pins

Once the SWD I/O is released by the user software, the GPIO controller takes control of
these pins. The reset states of the GPIO control registers put the I/Os in the equivalent
states:
●
SWDIO: alternate function pull-up
●
SWCLK: alternate function pull-down
Having embedded pull-up and pull-down resistors removes the need to add external
resistors.
5.3.4

SWD port connection with standard SWD connector

Figure 11
Figure 11. SWD port connection
CN9
FTSH-105-01-L-DV
SWD connector
20/29
shows the connection between the STM32F0xxx and a standard SWD connector.
10
9
8
7
6
5
4
3
2
1 VDD
Doc ID 023035 Rev 2
AN4080
NRST
SWCLK/PA14
SWDIO/PA13
STM32F05xx
MS30029V1