AT32F421 Series Reference Manual
2022.11.11 Page 83 Rev 2.02
6.2.3 General-purpose input configuration
When I/O port is configured as input:
Get I/O states by reading the input data register.
Support floating input, pull-up/pull-down input configuration.
Schmitt-trigger input is activated.
Output is disabled.
Note: In floating input mode, it is recommended to set the unused pins as analog input mode in order to
avoid leakage caused by interference from unused pins in a complex environment.
6.2.4 Analog input/output configuration
When I/O port is configured as analog input:
Schmitt-trigger input is disabled.
Digital input/output is disabled.
Without any pull-up/pull-down resistor.
6.2.5 General-purpose output configuration
Push-pull without
pull-up/pull-down
000: Output mode, normal sourcing/sinking strength
001: Output mode, large sourcing/sinking strength
010: Output mode, normal sourcing/sinking strength
011: Output mode, normal sourcing/sinking strength
1xx: Output mode, Maximum sourcing/sinking
strength
Open-drain without
pull-up/pull-down
000: Output mode, normal sourcing/sinking strength
001: Output mode, large sourcing/sinking strength
010: Output mode, normal sourcing/sinking strength
011: Output mode, normal sourcing/sinking strength
1xx: Output mode, Maximum sourcing/sinking
strength
When I/O port is configured as output:
Schmitt-trigger input is enabled
Output through output register
Pull-up/pull-down resistors are disabled
In open-drain mode, forced output 0, and use pull-up resistor to output 1
In push-pull mode, output 0/1 using output register
GPIO set/clear register is used to set or clear the corresponding GPIO data output register
Note: When writing 1 to the IOCB/IOSB bits of the GPIO set/clear register, IOSB has priority over
IOCB.
6.2.6 GPIO port protection
Locking mechanism is available to freeze the I/O configuration for the purpose of protection. When
LOCK is applied to a port bit, its configuration cannot be modified until the next reset or power on.
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