STM8S datasheet(107/467 Pages) STMICROELECTRONICS

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RM0016

General purpose I/O ports (GPIO)

113

11.3.1

Input modes

Clearing the DDRx bit selects input mode. In this mode, reading a IDR bit returns the digital

value of the corresponding I/O pin.

Refer to Section 11.7: Input mode details on page 109 for information on analog input,

external interrupts and Schmitt trigger enable/disable.

As shown in Table 21, four different input modes can be theoretically be configured by

software: floating without interrupt, floating with interrupt, pull-up without interrupt or pull-up

with interrupt. However in practice, not all ports have external interrupt capability or pull-ups.

You should refer to the datasheet pin-out description for details on the actual hardware

capability of each port.

Table 21. I/O port configuration summary

Mode

DDR

bit

CR1

bit

CR2

bit

Function

Pull-up

P-buffer

Diodes

to VDD

to VSS

Input

Floating without

interrupt

Off

Pull-up without

interrupt

Floating with interrupt

Off

Pull-up with interrupt

Output

Open drain output

Off

Push-pull output

Open drain output, fast

mode

Off

Push-pull, fast mode

Off

True open drain (on

specific pins)

Not implemented

Not im-

plemented

(1)

1. The diode connected to VDD is not implemented in true open drain pads. A local protection between the

pad and VOL is implemented to protect the device against positive stress.

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