Analog-to-Digital Converter (ADC)
Wait Mode
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0 Advance Information
MOTOROLA Analog-to-Digital Converter (ADC) 347
19.6 Wait Mode
The WAIT instruction can put the MCU in low power-consumption
standby 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 ADCH[4:0] in the ADC status and control
register before executing the WAIT instruction.
19.7 I/O Signals
The ADC module has 10 input signals that are shared with port B and
port C.
19.7.1 ADC Analog Power Pin (VDDAD)
The ADC analog portion uses VDDAD as its power pin. Connect the
VDDAD pin to the same voltage potential asVDD . External filtering may be
necessary to ensure clean VDDAD for good results.
NOTE: Route VDDAD carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
19.7.2 ADC Analog Ground Pin (VSSAD)
The ADC analog portion uses VSSAD as its ground pin. Connect the
VSSAD pin to the same voltage potential as VSS.
19.7.3 ADC Voltage Reference Pin (VREFH)
VREFH is the power supply for setting the reference voltage VREFH.
Connect the VREFH pin to the same voltage potential as VDDAD. There
will be a finite current associated with VREFH. See Section 22. Electrical
Specifications.
NOTE: Route VREFH carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.