s908qc16g0cdte Freescale Semiconductor, Inc, s908qc16g0cdte Datasheet - Page 97

• Manufacturer Part Number: s908qc16g0cdte
• Description: M68hc08 Family Of 8-bit Microcontroller Units Mcus
• Manufacturer: Freescale Semiconductor, Inc

Chapter 12
Input/Output Ports (PORTS)
12.1 Introduction
The MC68HC08QY1, MC68HC08QY2 and MC68HC08QY4 have thirteen bidirectional input-output (I/O)
pins and one input only pin. The MC68HC08QT1, MC68HC08QT2 and MC68HC08QT4 has five
bidirectional I/O pins and one input only pin. All I/O pins are programmable as inputs or outputs.
12.2 Unused Pin Termination
Input pins and I/O port pins that are not used in the application must be terminated. This prevents excess
current caused by floating inputs, and enhances immunity during noise or transient events. Termination
methods include:
Never connect unused pins directly to V
Since some general-purpose I/O pins are not available on all packages, these pins must be terminated
as well. Either method 1 or 2 above are appropriate.
12.3 Port A
Port A is an 6-bit special function port that shares its pins with the keyboard interrupt (KBI) module
(see
Chapter 14 Timer Interface Module
Converter (ADC10)
reset (RST) pin enabled using a configuration register (see
and the oscillator pins (see
Each port A pin also has a software configurable pullup device if the corresponding port pin is configured
as an input port.
Freescale Semiconductor
1. Configuring unused pins as outputs and driving high or low;
2. Configuring unused pins as inputs and enabling internal pull-ups;
3. Configuring unused pins as inputs and using external pull-up or pull-down resistors.
Chapter 9 Keyboard Interrupt Module
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 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.
Module), the external interrupt (IRQ) pin (see
Chapter 11 Oscillator Module
MC68HC08QY/QT Family Data Sheet, Rev. 2
(TIM)), the 10-bit ADC (see
DD
(KBI), the 2-channel timer interface module (TIM) (see
or V
SS
NOTE
.
(OSC)).
Chapter 5 Configuration Register
Chapter 3 10-Bit Analog-to-Digital
Chapter 8 External Interrupt
(CONFIG))
(IRQ)), the
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