ST7263BEX datasheet(43/186 Pages) STMICROELECTRONICS

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ST7263Bxx

I/O ports

Doc ID 7516 Rev 8

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I/O ports

9.1

Introduction

The I/O ports offer different functional modes:

●

Transfer of data through digital inputs and outputs and for specific pins

●

Analog signal input (ADC)

●

Alternate signal input/output for the on-chip peripherals

●

External interrupt generation

An I/O port consists of up to 8 pins. Each pin can be programmed independently as a digital

input (with or without interrupt generation) or a digital output.

9.2

Functional description

Each port is associated to 2 main registers:

●

Data register (DR)

●

Data Direction register (DDR)

Each I/O pin may be programmed using the corresponding register bits in DDR register: bit

X corresponding to pin X of the port. The same correspondence is used for the DR register.

Input modes

The input configuration is selected by clearing the corresponding DDR register bit.

In this case, reading the DR register returns the digital value applied to the external I/O pin.

Note:

All the inputs are triggered by a Schmitt trigger.

When switching from input mode to output mode, the DR register should be written first to

output the correct value as soon as the port is configured as an output.

Interrupt function

When an I/O is configured as an input with interrupt, an event on this I/O can generate an

external interrupt request to the CPU. The interrupt sensitivity is given independently

according to the description mentioned in the ITRFRE interrupt register.

Each pin can independently generate an interrupt request.

Each external interrupt vector is linked to a dedicated group of I/O port pins (see interrupts

section). If more than one input pin is selected simultaneously as an interrupt source, this is

logically ORed. For this reason if one of the interrupt pins is tied low, the other ones are

masked.

Table 10.

I/O pin functions

DDR

Mode

Input

Output

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