STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

General-purpose and alternate-function I/Os (GPIOs and AFIOs)
RM0008
Figure 17.
Alternate function configuration
To on-chip
peripheral
Alternate Function Input
Write
Read
Bit set/reset registers
Read/write
From on-chip
peripheral
Output data register
Input data register
Alternate Function Output
Input driver
Output driver
on
TTL Schmitt
trigger
Output
control
V DD
V SS
P-MOS
N-MOS
push-pull or
open-drain
V DD or V DD_FT (1)
VSS
Protection
diode
Protection
diode
I/O pin
ai14785
1. V DD_FT is a potential specific to five-volt tolerant I/Os and different from V DD .
8.1.10 Analog input configuration
When the I/O Port is programmed as Analog Input Configuration:
●
The Output Buffer is disabled.
● The Schmitt Trigger Input is de-activated providing zero consumption for every analog
value of the I/O pin. The output of the Schmitt Trigger is forced to a constant value (0).
● The weak pull-up and pull-down resistors are disabled.
● Read access to the Input Data Register gets the value “0”.
The Figure 18 on page 144 shows the High impedance-Analog Input Configuration of the
I/O Port bit.
Figure 18.
High impedance-analog input configuration
To on-chip
peripheral
Analog Input
Read
Write
Bit set/reset registers
Read/write
Output data register
Input data register
Input driver
0
off
TTL Schmitt
trigger
V DD or V DD_FT (1)
V SS
Protection
diode
Protection
diode
I/O pin
From on-chip
peripheral
ai14786
144/995 Doc ID 13902 Rev 9