AT32F425
Series Reference Manual
2022.03.30
Page 86
Ver 2.01
6.2.6
GPIO port protection
Locking mechanism can 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.
6.2.7
IOMUX structure
Several peripheral functions can be mapped on each IO pin. Peripheral input/output corresponding to
an I/O pin is selected through IOMUX input/output table. Each I/O pin has up to 8 IOMUX mapping
options for flexible selection, configured through the GPIOx_MUXL (for pin 0 to 7) and GPIOx_MUXH
(for pin 8 to 15) registers.
Each I/O pin is connected to only one peripheral’s pin by setting the GPIOx_MUXL or GPIOx_MUXH
register so that there can be no conflict between peripherals sharing the same pin.
While being used as multiplexed function input, the I/O port should be configured as input modes (floating,
pull-up and pull-down input)
To enable multiplexed function output, the port is configured as multiplexed function output mode
push-pull or open-drain mode by setting GPIOx_CFGR or GPIOx_OMODE register. In this case, the
pins are disconnected from GPIO controller, and controlled by IOMUX controller, instead.
To achieve bidirectional multiplexed function, the port needs to be configured as multiplexed function
output modes (push-pull or open-drain), controlled by IOMUX controller.
Figure 6-2 IOM UX structure
IO
ESD
protect
SMT trigger
PU
PD
output data
output enable
input enable
input data
push/pull
strength control
analog input/output
AH
B
b
u
s
IO
M
U
X
co
n
tro
l
Single IO
Analog
module
Peripheral
Module
6.2.8
Multiplexed function pull-up/down configuration
Mode
IOMC
PUPD
Multiplexed function floating
10
00
Multiplexed function pull-down
10
Multiplexed function pull-up
01
When an I/O port is configured as input:
Get an I/O pin state by reading input data registers
The pin be configured as floating input, pull-up or pull-down input
Schmitt-trigger input is activated.
GPIO pin output is disabled.