MC68HC908QB8 Datasheet, PDF (103/236 Pages) Freescale Semiconductor, Inc – To provide the most up-to-date information, the revision of our documents

Chapter 12
Input/Output Ports (PORTS)
12.1 Introduction
The MC68HC908QB8, MC68HC908QB4 and MC68HC908QY8 have thirteen bidirectional pins and one
input only pin.
NOTE
Connect any unused I/O pins to an appropriate logic level, either V_DD or V_SS.
Although the I/O ports do not require termination for proper operation,
termination reduces excess current consumption and the possibility of
electrostatic damage.
12.2 Port A
Port A is an 6-bit special function port that shares its pins with the keyboard interrupt (KBI) module
(see Chapter 9 Keyboard Interrupt Module (KBI), the 4-channel timer interface module (TIM) (see Chapter
16 Timer Interface Module (TIM)), the 10-bit ADC (see Chapter 3 Analog-to-Digital Converter (ADC10)
Module), the external interrupt (IRQ) pin (see Chapter 8 External Interrupt (IRQ)), the reset (RST) pin
enabled using a configuration register (see Chapter 5 Configuration Register (CONFIG)) and the
oscillator pins (see Chapter 11 Oscillator Module (OSC)).
Each port A pin also has a software configurable pullup device if the corresponding port pin is configured
as an input port.
PTA2 is input only.
NOTE
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 logic 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.
MC68HC908QB8 Data Sheet, Rev. 1
Freescale Semiconductor
103