Datasheet

General Description
MC68HC908QYA/QTA Family Data Sheet, Rev. 3
20 Freescale Semiconductor
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.
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.
Table 1-3. Function Priority in Shared Pins
Pin Name Highest-to-Lowest Priority Sequence
PTA0
(1)
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.
AD0 → TCH0 → KBI0 → PTA0
PTA1
(1)
AD1 → TCH1 → KBI1 → PTA1
PTA2 IRQ → TCLK → KBI2 → PTA2
PTA3 RST
→ KBI3 → PTA3
PTA4
(1)
OSC2 → AD2 → KBI4 → PTA4
PTA5
(1)
OSC1 → AD3 → KBI5 → PTA5
PTB0
(1)
AD4 → PTB0
PTB1
(1)
AD5 → PTB1