ST92196A datasheet(13/268 Pages) STMICROELECTRONICS

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GENERAL DESCRIPTION

PIN DESCRIPTION (Cont’d)

1.2.1 I/O Port Configuration

All ports can be individually configured as input, bi-

directional, output, or alternate function. Refer to

the Port Bit Configuration Table in the I/O Port

Chapter.

No I/O pins have any physical weak pull-up capa-

bility (they will show no pull-up if they are pro-

grammed in the "weak pull-up" software mode).

Input levels can be selected on a bit basis by

choosing between TTL or CMOS input levels for I/

O port pin except for P2.(5:4,0), P3.(6:3,1:0),

P4.(1:0) which are implemented with a Schmitt

trigger function.

All port output configurations can be software se-

lected on a bit basis to provide push-pull or open

drain driving capabilities. For all ports, when con-

figured as open-drain, the voltage on the pin must

never exceed the VDD power line value (refer to

Electrical characteristics section).

1.2.2 I/O Port Reset State

I/Os are reset asynchronously as soon as the RE-

SET pin is asserted low.

All I/O are forced by the Reset in bidirectional, high

impedance output due to the lack of physical pull-

up except P5.0 (refer to the Reset section) which

is forced into the "Push-Pull Alternate Function"

mode until being reconfigured by software.

Warning

When a common pin is declared to be connected

to an alternate function input and to an alternate

function output, the user must be aware of the fact

that the alternate function output signal always in-

puts to the alternate function module declared as

input.

When any given pin is declared to be connected to

a digital alternate function input, the user must be

aware of the fact that the alternate function input is

always connected to the pin. When a given pin is

declared to be connected to an analog alternate

function input (ADC input for example) and if this

pin is programmed in the "AF-OD" mode, the digit-

al input path is disconnected from the pin to pre-

vent any DC consumption.

Table 3. I/O Port Characteristics

Legend: OD = Open Drain, AF = Alternate Function

Input

Output

Weak Pull-Up

Reset State

Port 0[7:0]

TTL/CMOS

Push-Pull/OD

Bidirectional

Port 2.0

Port 2[3:1]

Port 2[5:4]

Port 2[7:6]

Schmitt trigger

TTL/CMOS

Schmitt trigger

TTL/CMOS

Push-Pull/OD

Bidirectional

Port 3.0

Port 3.1

Port 3.2

Port 3[6:3]

Port 3.7

Schmitt trigger

TTL/CMOS

Schmitt trigger

TTL/CMOS

Push-Pull/OD

Bidirectional

Port 4.[1:0]

Port 4.[7:2]

Schmitt trigger

TTL/CMOS

Push-Pull/OD

Bidirectional

Port 5.0

Port 5[6:1]

TTL/CMOS

Push-Pull/OD

Push-Pull AF Out

Bidirectional

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