Output Configuration; Figure 19. Input Floating/Pull Up/Pull Down Configurations - ST STM32F412 Reference Manual

RM0402
Read
Write
Read/write
7.3.10

Output configuration

When the I/O port is programmed as output:
• The output buffer is enabled:
–
–
•
The Schmitt trigger input is activated
•
The weak pull-up and pull-down resistors are activated or not 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 AHB1
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 20

Figure 19. Input floating/pull up/pull down configurations

input driver
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
shows the output configuration of the I/O port bit.
on
TTL Schmitt
trigger
RM0402 Rev 6
General-purpose I/Os (GPIO)
V DD
V DD
on/off
protection
diode
pull
up
on/off
protection
pull
diode
down
V SS
V SS
I/O pin
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