Output Configuration; Alternate Function Configuration; Figure 19. Output Configuration - ST STM32F410 Reference Manual

RM0401
6.3.10

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 19
6.3.11

Alternate function configuration

When the I/O port is programmed as alternate function:
•
The output buffer can be configured as open-drain or push-pull
•
The output buffer is driven by the signal coming from the peripheral (transmitter enable
and data)
•
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
Figure 20
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.

Figure 19. Output configuration

shows the Alternate function configuration of the I/O port bit.
RM0401 Rev 3
General-purpose I/Os (GPIO)
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