MC68HC908QY4A_10 Datasheet, PDF (20/200 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

General Description
1.6 Pin Function Priority
Table 1-3 is meant to resolve the priority if multiple functions are enabled on a single pin.
NOTE
Upon reset all pins come up as input ports regardless of the priority table.
Table 1-3. Function Priority in Shared Pins
Pin Name
PTA0⁽¹⁾
PTA1⁽¹⁾
PTA2
PTA3
PTA4⁽¹⁾
PTA5⁽¹⁾
PTB0⁽¹⁾
PTB1⁽¹⁾
Highest-to-Lowest Priority Sequence
AD0 → TCH0 → KBI0 → PTA0
AD1 → TCH1 → KBI1 → PTA1
IRQ → TCLK → KBI2 → PTA2
RST → KBI3 → PTA3
OSC2 → AD2 → KBI4 → PTA4
OSC1 → AD3 → KBI5 → PTA5
AD4 → PTB0
AD5 → PTB1
1. When a pin is to be used as an ADC pin, the I/O port function should be left as
an input and all other shared modules should be disabled. The ADC does not
override additional modules using the pin.
1.7 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:
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.
Never connect unused pins directly to V_DD or V_SS.
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.
MC68HC908QYA/QTA Family Data Sheet, Rev. 3
20
Freescale Semiconductor