MC908QT4MPE datasheet(97/184 Pages) FREESCALE

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MC68HC908QY/QT Family Data Sheet, Rev. 5

Freescale Semiconductor

Chapter 12

Input/Output Ports (PORTS)

12.1 Introduction

The MC68HC908QT1, MC68HC908QT2, and MC68HC908QT4 have five bidirectional input-output (I/O)

pins and one input only pin. The MC68HC908QY1, MC68HC908QY2, and MC68HC908QY4 have

thirteen bidirectional pins and one input only pin. All I/O pins are programmable as inputs or outputs.

NOTE

Connect any unused I/O pins to an appropriate logic level, either V

DD or VSS.

Although the I/O ports do not require termination for proper operation,

termination reduces excess current consumption and the possibility of

electrostatic damage.

8-pin devices have non-bonded pins. These pins should be configured

either as outputs driving low or high, or as inputs with internal pullups

enabled. Configuring these non-bonded pins in this manner will prevent any

excess current consumption caused by floating inputs.

12.2 Port A

Port A is a 6-bit special function port that shares all six of its pins with the keyboard interrupt (KBI) module

(see Chapter 9 Keyboard Interrupt Module (KBI)). Each port A pin also has a software configurable pullup

device if the corresponding port pin is configured as an input port.

NOTE

PTA2 is input only.

When the IRQ function is enabled in the configuration register 2

(CONFIG2), bit 2 of the port A data register (PTA) will always read a 0. In

this case, the BIH and BIL instructions can be used to read the logic level

on the PTA2 pin. When the IRQ function is disabled, these instructions will

behave as if the PTA2 pin is a logic 1. However, reading bit 2 of PTA will

read the actual logic level on the pin.

MC908QT4MPE Datasheet(PDF) 97 Page - Freescale Semiconductor, Inc