ST7L19 datasheet(47/138 Pages) STMICROELECTRONICS

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ST7L15, ST7L19

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I/O PORTS (cont’d)

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.

WARNING: The analog input voltage level must

be within the limits stated in the absolute maxi-

mum ratings.

10.3 I/O PORT IMPLEMENTATION

The hardware implementation on each I/O port de-

pends 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 anoth-

er should be done in a sequence that prevents un-

wanted side effects. Recommended safe transi-

tions are illustrated in Figure 30. Other transitions

are potentially risky and should be avoided, since

they may present unwanted side-effects such as

spurious interrupt generation.

Figure 30. Interrupt I/O Port State Transitions

10.4 UNUSED I/O PINS

Unused I/O pins must be connected to fixed volt-

age levels. Refer to section 13.8 on page 113.

10.5 LOW-POWER MODES

10.6 INTERRUPTS

The external interrupt event generates an interrupt

if the corresponding configuration is selected with

DDR and OR registers and if the I bit in the CC

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