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MC68HC08AS32A Datasheet, PDF (57/296 Pages) Motorola, Inc – Microcontrollers
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Freescale Semiconductor, Inc.
Analog-to-Digital Converter (ADC)
I/O Signals
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 18.7 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.
3.7 I/O Registers
These I/O registers control and monitor ADC operation:
• ADC status and control register (ADSCR)
• ADC data register (ADR)
• ADC input clock register (ADICLK)
MC68HC08AS32A — Rev. 1
MOTOROLA
Analog-to-Digital Converter (ADC)
For More Information On This Product,
Go to: www.freescale.com
Data Sheet
57
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