Input Configuration; Output Configuration; Figure 45. Input Floating/Pull-Up/Pull-Down Configurations - ST STM32WL5 Series Reference Manual

RM0453
10.3.9

Input configuration

When the I/O port is programmed as input, the following occurs:
•
The output buffer is disabled.
•
The Schmitt trigger input is activated.
•
The pull-up and pull-down resistors are activated depending on the value in the
GPIOx_PUPDR register.
•
The data present on the I/O pin are sampled into the input data register every AHB
clock cycle.
•
A read access to the input data register provides the I/O state.
The figure below shows the input configuration of the I/O port bit.
Read
Write
Read/write
10.3.10

Output configuration

When the I/O port is programmed as output, the following occurs:
•
The output buffer is enabled:
–
–
• The Schmitt trigger input is activated.
•
The pull-up and pull-down resistors are activated depending on the value in the
GPIOx_PUPDR register.
•
The data present on the I/O pin are sampled into the input data register every AHB
clock cycle.
•
A read access to the input data register gets the I/O state.
•
A read access to the output data register gets the last written value.

Figure 45. Input floating/pull-up/pull-down configurations

output driver
Open drain mode: A 0 in the Output register activates the N-MOS whereas a 1 in
the Output register leaves the port in Hi-Z (the P-MOS is never activated).
Push-pull mode: A 0 in the Output register activates the N-MOS whereas a 1 in the
Output register activates the P-MOS.
on
TTL Schmitt
trigger
input driver
RM0453 Rev 1
General-purpose I/Os (GPIO)
V DDIOx
V DDIOx
on/off
protection
diode
pull
up
on/off
protection
pull
diode
down
V SS
V SS
MS31477V1
I/O pin
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