MC908QL4ME View Datasheet(PDF) - Freescale Semiconductor

Part Name

Description

Manufacturer

MC908QL4ME

M68HC08 Microcontrollers

Freescale Semiconductor 

General Description

1.5 Pin Function Priority

Table 1-2 defines the priority of a shared pin if multiple functions are enabled. Only the shared pins are

shown in the table.

Table 1-2. Function Priority in Shared Pins

Pin Name

PTA0(1)

PTA1(1)

PTA2

Highest-to-Lowest Priority Sequence

AD0 → TCH1 → KBI0 → PTA0

AD1 → KBI1 → PTA1

TCLK → IRQ → KBI2 → PTA2(2)

PTA3

PTA4(1)

PTA5(1)

RST → KBI3 → PTA3

OSC2 → AD2 → KBI4 → PTA4

OSC1 → AD3 → KBI5 → PTA5

PTB0

TCH0 → PTB0

PTB1

PTB2(1)

PTB3(1)

PTB1

AD4 → PTB2

AD5 → PTB3

PTB4

SLCRx → PTB4

PTB5

SLCTx → PTB5

1. When a pin is to be used as an ADC pin, the I/O port function should be

left as an input. The ADC does not override the port data direction

register.

2. TCLK is not included in the priority scheme. When TCLK is enabled the

other shared functions in the pin should be disabled.

1.6 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 VDD or VSS.

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.

MC68HC908QL4 Data Sheet, Rev. 7

24

Freescale Semiconductor

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