ST7LITEUSX datasheet(42/108 Pages) STMICROELECTRONICS

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ST7LITEUSx

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occur)

– select falling edge

– disable the external interrupt through the OR

– select rising edge

9.2.2 Output Modes

The output configuration is selected by setting the

corresponding DDR register bit. In this case, writ-

ing the DR register applies this digital value to the

I/O pin through the latch. Then reading the DR reg-

ister returns the previously stored value.

Two different output modes can be selected by

software through the OR register: Output push-pull

and open-drain.

DR register value and output pin status:

Note: When switching from input to output mode,

the DR register has to be written first to drive the

correct level on the pin as soon as the port is con-

figured as an output.

9.2.3 Alternate Functions

When an on-chip peripheral is configured to use a

pin, the alternate function is automatically select-

ed. This alternate function takes priority over the

standard I/O programming under the following

conditions:

– When the signal is coming from an on-chip pe-

ripheral, the I/O pin is automatically configured in

output mode (push-pull or open drain according

to the peripheral).

– When the signal is going to an on-chip peripher-

al, the I/O pin must be configured in floating input

mode. In this case, the pin state is also digitally

readable by addressing the DR register.

Notes:

– Input pull-up configuration can cause unexpect-

ed value at the input of the alternate peripheral

input.

– When an on-chip peripheral use a pin as input

and output, this pin has to be configured in input

floating mode.

Push-pull

Open-drain

0VSS

Vss

1VDD

Floating

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