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Structure block diagram
Figure 13 5V GPIO-compatible Structure Block Diagram
Bit set/clear
register
Output
control
Output data
register
V
DD
V
SS
Input data
register
V
DD
V
SS
V
DD_FT
(1)
V
SS
TTL Schottky
trigger
Analog input
Multiplexing function input
To on-chip
peripheral
Read
Read-write
Multiplexing function output
From on-chip
peripheral
Push-pull, open-
drain, disable
P-MOS
N-MOS
I/O pin
Write
(1) V
DD _FT
is different from V
DD
, and V
DD _FT
is special for FT GPIO pin.
Functional description
Each pin of GPIO can be configured as pull-up, pull-down, floating and analog
input, or push-pull/open-drain output input mode and multiplexing function
through software. All GPIO interfaces have external interrupt capability.
IO status during reset and just after reset
If the multiplexing function is not enabled during and after GPIO reset, the I/O
port will be configured as floating input mode, and in such case the pull-up/pull-
down resistor is disabled in input mode. After reset, the JTAG pin is put in the
input pull-up or pull-down mode, and the specific configuration is as follows:
PA15: JTDI in pull-up mode
PA14: JTCK in pull-down mode
PA13: JTMS in pull-up mode
PB4: JNTRST in pull-up mode
PB3: JTDO is put in floating mode
Input mode
In the input mode, it can be set as pull-up, pull-down, floating and analog input.
When GPIO is configured as input mode, all GPIO pins have internal weak pull-
up and weak pull-down resistors, which can be activated or disconnected.
Pull-up, pull-down, and floating modes