AN432/1203

1/12

Rev. 1.1

AN432

APPLICATION NOTE

USING ST62xx I/O PORTS SAFELY

by J.Stockinger

INTRODUCTION

All members of the ST62 Series of Microcontrollers from STMicroelectronics feature I/O ports

with configurable bit functions. In addition many I/O bits may be set as inputs to the on-chip

Analog to Digital Converter. This port bit function is in addition to the normal I/O functions of

input (with or without internal pull-up resistor), output (open drain or push-pull) or edge/level

selectable interrupt input (with pull-up). This flexibility makes the ST62 series suitable for

many industrial control applications (and for many other uses).

This application note explains the architecture of the I/O bit associated with these port func-

tions and provides some indications on the correct use of these features for functions such as

keyboard scanning and analog inputs. The correct manner to switch between these function is

also demonstrated in order to prevent potential malfunctions in operation.

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