I/O ports ST7LITE49M
10.2.4 Analog alternate function
Configure the I/O as floating input to use an ADC input. The analog multiplexer (controlled by the ADC registers) switches the analog voltage present on the selected pin to the common analog rail, connected to the ADC input.
Analog Recommendations
Do not change the voltage level or loading on any I/O while conversion is in progress. Do not have clocking pins located close to a selected analog pin.
Caution: The analog input voltage level must be within the limits stated in the absolute maximum ratings.
10.3 I/O port implementation
The hardware implementation on each I/O port depends on the settings in the DDR and OR registers and specific I/O port features such as ADC input or open-drain.
Switching these I/O ports from one state to another should be done in a sequence that
prevents unwanted side effects. Recommended safe transitions are illustrated in Figure 35 .
Other transitions are potentially risky and should be avoided, since they may present unwanted side-effects such as spurious interrupt generation.
Figure 35.
Interrupt I/O port state transitions
01 00
INPUT floating/pull-up interrupt
INPUT floating
(reset state)
10
OUTPUT open-drain
XX = DDR, OR
11
OUTPUT push-pull
10.4 Unused I/O pins
Unused I/O pins must be connected to fixed voltage levels. Refer to
Section 13.9: I/O port pin characteristics .
10.5 Low power modes
s
Table 26.
Effect of low power modes on I/O ports
Mode Description
Wait
Halt
No effect on I/O ports. External interrupts cause the device to exit from Wait mode.
No effect on I/O ports. External interrupts cause the device to exit from Halt mode.
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