MC68HC908QY4_10 Datasheet, PDF (97/168 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

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 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.
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.
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 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.
MC68HC908QY/QT Family Data Sheet, Rev. 6
Freescale Semiconductor
97