MC68HC908GR4MP datasheet(25/286 Pages) FREESCALE

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Pin Functions

MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7

Freescale Semiconductor

1.5.6 External Filter Capacitor Pin (CGMXFC)

CGMXFC is an external filter capacitor connection for the CGM. See Chapter 7 Clock Generator Module

(CGMC).

1.5.7 Analog Power Supply/Reference Pins (VDDAD/VREFH and VSSAD/VREFL)

VDDAD and VSSAD are the power supply pins for the analog-to-digital converter. Decoupling of these pins

should be as per the digital supply.

NOTE

VREFH is the high reference supply for the ADC. The VREFH signal is

internally connected with VDDAD and have the same potential as VDDAD.

VDDAD should be tied to the same potential as VDD via separate traces.

VREFL is the low reference supply for the ADC. The VREFL pin is internally

connected with VSSAD and has the same potential as VSSAD. VSSAD should

be tied to the same potential as VSS via separate traces.

See Chapter 5 Analog-to-Digital Converter (ADC).

1.5.8 Port A Input/Output (I/O) Pins (PTA3/KBD3–PTA0/KBD0)

PTA3–PTA0 are special-function, bidirectional I/O port pins. Any or all of the port A pins can be

programmed to serve as keyboard interrupt pins. See Chapter 16 Input/Output Ports (I/O) and See

Chapter 12 External Interrupt (IRQ).

These port pins also have selectable pullups when configured for input mode. The pullups are disengaged

when configured for output mode. The pullups are selectable on an individual port bit basis.

When the port pins are configured for special-function mode (KBI), pullups will be automatically engaged.

As long as the port pins are in special-function mode, the pullups will always be on.

1.5.9 Port B I/O Pins (PTB5/AD5–PTB0/AD0)

PTB5–PTB0 are special-function, bidirectional I/O port pins that can also be used for analog-to-digital

converter (ADC) inputs. See Chapter 16 Input/Output Ports (I/O) and See Chapter 5 Analog-to-Digital

Converter (ADC).

There are no pullups associated with this port.

1.5.10 Port C I/O Pins (PTC1–PTC0)

PTC1–PTC0 are general-purpose, bidirectional I/O port pins. See Chapter 16 Input/Output Ports (I/O).

PTC0 and PTC1 are only available on 32-pin QFP packages.

These port pins also have selectable pullups when configured for input mode. The pullups are disengaged

when configured for output mode. The pullups are selectable on an individual port bit basis.

1.5.11 Port D I/O Pins (PTD6/T2CH0–PTD0/SS)

PTD6–PTD0 are special-function, bidirectional I/O port pins. PTD3–PTD0 can be programmed to be

serial peripheral interface (SPI) pins, while PTD6–PTD4 can be individually programmed to be timer

interface module (TIM1 and TIM2) pins. See Chapter 22 Timer Interface Module (TIM), Chapter 20 Serial

Peripheral Interface (SPI), and See Chapter 16 Input/Output Ports (I/O).

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