Output Configuration; Alternate Function Configuration; Figure 19. Output Configuration - ST STM32G0 1 Series Reference Manual

General-purpose I/Os (GPIO)
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 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 19
To / from on-chip
peripherals,
power control
and EXTI
Read
Write
Read/write
7.3.11

Alternate function configuration

When the I/O port is programmed as alternate function:
•
The output buffer can be configured in open-drain or push-pull mode
•
The output buffer is driven by the signals 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 AHB
clock cycle
•
A read access to the input data register gets the I/O state
Figure 20
238/1390
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

Analog input/output
Input driver
Output driver
shows the Alternate function configuration of the I/O port bit.
On
TTL Schmitt trigger
V
DDIOx
P-MOS
Output
control
N-MOS
V
SS
RM0444 Rev 5
V
DDIOx
on/off
Pull
up
on/off
Pull
down
V
SS
Push-pull or
open-drain
RM0444
I/O pin
MSv33184V3