ST72411R datasheet(28/71 Pages) STMICROELECTRONICS

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ST72411R

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I/O PORTS (Cont’d)

Smartcard versus Standard I/Os

The Smartcard I/O ports differ from the standard I/

O ports in that they have a different power supply:

the output buffers and the input Schmitt trigger are

supplied by VSC_PWR for the Smartcard I/Os and

by VDD for the Standard I/Os. For Smartcard I/Os,

the Schmitt trigger is designed to guarantee output

levels compatible with VDD for VSC_PWR =5V or

3V.

Caution: When the SSS regulator is deactivated

(bit SSSEN=0), the Smartcard I/O ports cannot be

used correctly (VSC_PWR=VSS). In this case,

special care is required when manipulating exter-

nal interrupts: As Smartcard I/Os are always tied

to ground, they may mask interrupts on other I/O

lines of the same port.

Figure 21. I/O Block Diagram

Table 6. Port Mode Options

NI - not implemented

Off - implemented not activated

On - implemented and activated

DDR

PAD

VDD or VSC_PWR

ALTERNATE

ENABLE

ALTERNATE

OUTPUT

OR SEL

DDR SEL

DR SEL

INTERRUPT

PULL-UP

CONDITION

P-BUFFER

(OPTION*)

N-BUFFER

PULL-UP

(OPTION*)

* SEE TABLE BELOW

ANALOG

INPUT

If implemented

ALTERNATE

INPUT

VDD or VSC_PWR

DIODES

(OPTION*)

PULL-DOWN

CONDITION

Configura tion Mode

Pull-Up

P-Buffer

Diodes

Input

Floating

Off

Pull-up with Interrupt

Output

Push-pull

Off

Open Drain (logic level)

Off

Push-pull with pull-up

Open Drain (logic level) with pull-up

Off

True Open Drain

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