MC908GZ60CFUE Datasheet, PDF (67/352 Pages) Freescale Semiconductor, Inc – Standard features, Features of the CPU08

I/O Registers
3.7.3 ADC Voltage Reference High Pin (V_REFH)
The ADC analog portion uses V_REFH as its upper voltage reference pin. By default, connect the V_REFH
pin to the same voltage potential as V_DD. External filtering is often necessary to ensure a clean V_REFH for
good results. Any noise present on this pin will be reflected and possibly magnified in A/D conversion
values.
NOTE
For maximum noise immunity, route V_REFH carefully and place bypass
capacitors as close as possible to the package. Routing V_REFH close and
parallel to V_REFL may improve common mode noise rejection.
V_DDAD and V_REFH are bonded internally.
3.7.4 ADC Voltage Reference Low Pin (V_REFL)
The ADC analog portion uses V_REFL as its lower voltage reference pin. By default, connect the V_REFL pin
to the same voltage potential as V_SS. External filtering is often necessary to ensure a clean V_REFL for good
results. Any noise present on this pin will be reflected and possibly magnified in A/D conversion values.
NOTE
For maximum noise immunity, route V_REFL carefully and, if not connected
to V_SS, place bypass capacitors as close as possible to the package.
Routing V_REFH close and parallel to V_REFL may improve common mode
noise rejection.
V_SSAD and V_REFL are bonded internally.
3.7.5 ADC Voltage In (V_ADIN)
V_ADIN is the input voltage signal from one of the 24 ADC channels to the ADC module.
3.8 I/O Registers
These I/O registers control and monitor ADC operation:
• ADC status and control register (ADSCR)
• ADC data register (ADRH and ADRL)
• ADC clock register (ADCLK)
MC68HC908GZ60 • MC68HC908GZ48 • MC68HC908GZ32 Data Sheet, Rev. 6
Freescale Semiconductor
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