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In (pull-up, pull-down, floating) input mode
Schmitt trigger is opened
Disable output buffer
Connect weak pull-up and pull-down resistors according to different
input configurations
The input data register GPIOx_IDATA captures the data on I/O pin in
each AHB1 clock cycle
Read I/O state through the input data register GPIOx_IDATA
The initial level state of the floating input mode is uncertain and is easy to be
disturbed by the outside; when connecting the equipment, it is determined by
the external input level (except for the very high impedance).
The initial level state of pull-up/pull-down input mode is high level if pull-up, and
low level if pull-down; when connecting the equipment, it is determined by the
external input level and load impedance.
Analog input mode
In analog input mode
Disable output buffer
The input of Schmitt trigger is disabled, and the output value of
Schmitt trigger is forced to be 0
Weak pull-up and pull-down resistors are disabled
The value of port input state register is 0
Figure 14 Input Mode Structure
Input data
register
TTL Schottky
trigger
Analog input
Multiplexing function input
To on-chip
peripheral
Read
I/O pin
V
DD
V
DD
V
SS
V
SS
Output mode
In the output mode, it can be set as push-pull output and open-drain output.
When GPIO is configured as the output pin, the output speed of the port can be
configured and the output drive mode (push-pull / open-drain) can be selected.
In output mode
Schmitt trigger is opened,
Activate output buffer
Weak pull-up and pull-down resistors are disabled