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AN4206

Debug management

4.3.1

SWJ debug port pins

Five pins are used as outputs for the SWJ-DP as alternate functions of general-purpose

I/Os (GPIOs). These pins, shown in Table 2, are available on all packages.

4.3.2

Flexible SWJ-DP pin assignment

After reset (SYSRESETn or PORESETn), all five pins used for the SWJ-DP are assigned as

dedicated pins immediately usable by the debugger host (note that the trace outputs are not

assigned except if explicitly programmed by the debugger host).

However, some of the JTAG pins shown in Table 3 can be configured to an alternate

function through the GPIOx_AFRx registers.

Table 3 shows the different possibilities to free some pins to be configured alternate

functions.

For more details, see the corresponding STM32F3xx reference manual (RM0316, RM0313,

RM0365 and RM0366) available from the STMicroelectronics website www.st.com.

Table 2. Debug port pin assignment

SWJ-DP pin name

JTAG debug port

SW debug port

assignment

Type

Description

Type

Debug assignment

JTMS/SWDIO

JTAG test mode

selection

I/O

Serial wire data

input/output

PA13

JTCK/SWCLK

JTAG test clock

Serial wire clock

PA14

JTDI

JTAG test data input

PA15

JTDO/TRACESWO

JTAG test data

output

TRACESWO if async

trace is enabled

PB3

JNTRST

JTAG test nReset

PB4

Table 3. SWJ I/O pin availability

Available Debug ports

SWJ I/O pin assigned

PA13 /

JTMS/

SWDIO

PA14 /

JTCK/

SWCLK

PA15 /

JTDI

PB3 /

JTDO

PB4/

JNTRST

Full SWJ (JTAG-DP + SW-DP) - reset state

Full SWJ (JTAG-DP + SW-DP) but without

JNTRST

JTAG-DP disabled and SW-DP enabled

JTAG-DP disabled and SW-DP disabled

Free to be configured as alternate functions

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