ST72324BK2 datasheet(57/188 Pages) STMICROELECTRONICS

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ST72324B

I/O ports

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Analog alternate function

When the pin is used as an ADC input, the I/O must be configured as floating input. The

analog multiplexer (controlled by the ADC registers) switches the analog voltage present on

the selected pin to the common analog rail which is connected to the ADC input.

It is recommended not to change the voltage level or loading on any port pin while

conversion is in progress. Furthermore it is recommended not to have clocking pins located

close to a selected analog pin.

Warning:

The analog input voltage level must be within the limits

stated in the absolute maximum ratings.

9.3

I/O port implementation

The hardware implementation on each I/O port depends on the settings in the DDR and OR

registers and specific feature of the I/O port such as ADC Input or true 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 31.

Other transitions are potentially risky and should be avoided, since they are likely to present

unwanted side-effects such as spurious interrupt generation.

Figure 31.

Interrupt I/O port state transitions

9.4

Low power modes

9.5

Interrupts

The external interrupt event generates an interrupt if the corresponding configuration is

selected with DDR and OR registers and the interrupt mask in the CC register is not active

(RIM instruction).

floating/pull-up

interrupt

Input

floating

(reset state)

Input

open-drain

Output

push-pull

Output

= DDR, OR

Table 29.

Effect of low power modes on I/O ports

Mode

Description

Wait

No effect on I/O ports. External interrupts cause the device to exit from Wait mode.

Halt

No effect on I/O ports. External interrupts cause the device to exit from Halt mode.

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