MC68HC08AS32 Datasheet, PDF(49/280 Page) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

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MC68HC08AS32 Datasheet, PDF (49/280 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

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logic 0. The COCO bit is not used as a conversion complete flag when interrupts

are enabled.

3.5 Low-Power Modes

The following paragraphs describe the low-power modes.

3.5.1 Wait Mode

The ADC continues normal operation during wait mode. Any enabled CPU interrupt

request from the ADC can bring the MCU out of wait mode. If the ADC is not

required to bring the MCU out of wait mode, power down the ADC by setting the

ADCH[4:0] bits in the ADC status and control register to logic 1s before executing

the WAIT instruction.

3.5.2 Stop Mode

The ADC module is inactive after the execution of a STOP instruction. Any pending

conversion is aborted. ADC conversions resume when the MCU exits stop mode.

Allow one conversion cycle to stabilize the analog circuitry before attempting a new

ADC conversion after exiting stop mode.

3.6 I/O Signals

The ADC module has 15 channels that are shared with I/O ports B and D and one

channel with an input-only port bit on port D. Refer to 17.6 ADC Characteristics

for voltages referenced in the next three subsections.

3.6.1 ADC Analog Power Pin (VDDA/VDDAREF)/ADC Voltage Reference Pin (VREFH)

The ADC analog portion uses VDDA/VDDAREF as its power pin. Connect the

VDDA/VDDAREF pin to the same voltage potential as VDD. External filtering may be

necessary to ensure clean VDDA/VDDAREF for good results.

VREFH is the high reference voltage for all analog-to-digital conversions.

NOTE: Route VDDA/VDDAREF carefully for maximum noise immunity and place bypass

capacitors as close as possible to the package.

3.6.2 ADC Analog Ground Pin (VSSA)/ADC Voltage Reference Low Pin (VREFL)

The ADC analog portion uses VSSA as its ground pin. Connect the VSSA pin to the

same voltage potential as VSS. VREFL is the lower reference supply for the ADC.

3.6.3 ADC Voltage In (ADCVIN)

ADCVIN is the input voltage signal from one of the 15 ADC channels to the ADC

module.

MC68HC08AS32 â Rev. 4.1

Freescale Semiconductor

Data Sheet

49

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