ST STM32WL55JC Reference Manual page 395

RM0453
MODE(i)[1:0] OTYPER(i)
00
11
1. GP = general purpose, PP = push-pull, PU = pull-up, PD = pull-down, OD = open drain, AF = alternate function.
10.3.1 General purpose I/O (GPIO)
During and just after reset, the alternate functions are not active and most of the I/O ports
are configured in input analog mode.
The debug pins listed below are in AF pull-up/pull-down after reset:
•
PA15: JTDI in input mode with pull-up
•
PA14: JTCK/SWCLK in input mode with pull-down
•
PA13: JTMS/SWDAT in input mode with pull-up
•
PB4: NJTRST in input mode with pull-up
•
PB3: JTDO in HI-Z mode no pulls.
PH3/BOOT0 is in input mode during the reset until at least the end of the option byte loading
phase (see
When the I/O pin is configured as output, the value written to the output data register
GPIOx_ODR is output on the I/O pin. It is possible to use the output driver in push-pull mode
or open-drain mode (only the low level is driven, high level is HI-Z).
The input data register GPIOx_IDR captures the data present on the I/O pin at every AHB
clock cycle.
All GPIO pins have weak internal pull-up and pull-down resistors, which can be activated or
not depending on the value in the GPIOx_PUPDR register.
10.3.2 I/O pin alternate function multiplexer and mapping
The I/O pins are connected to on-board peripherals/modules through a multiplexer that
allows only one AF peripheral connected to each I/O pin at a time. This avoids conflict
between peripherals available on the same I/O pin.
Each I/O pin has a multiplexer with up to sixteen alternate function inputs (AF0 to AF15),
that can be configured through the registers GPIOx_AFRL (for pin 0 to 7) and GPIOx_AFRH
(for pin 8 to 15):
After reset, the multiplexer selection is alternate function 0 (AF0). I/Os are configured in
alternate function mode through GPIOx_MODER register.
Table 70. Port bit configurations (continued)
OSPEED(i)[1:0]
X XX
X XX
X XX
X XX
X XX
X XX
X XX
X XX
Section 10.3.15: Using PH3 as
PUPD(i)[1:0]
00
01
10
11
00
01
10
11
GPIO).
RM0453 Rev 2
General-purpose I/Os (GPIO)
(1)
I/O configuration
Input Floating
Input PU
Input PD
Reserved (input floating)
Input/output Analog
Reserved
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