
Functional Description
MC68HC908GR16 Data Sheet, Rev. 5.0
Freescale Semiconductor
49
Figure 3-2. ADC Block Diagram
3.3.2 Voltage Conversion
When the input voltage to the ADC equals VREFH, the ADC converts the signal to $3FF (full scale). If the
input voltage equals VREFL, the ADC converts it to $000. Input voltages between VREFH and VREFL are a
straight-line linear conversion.
NOTE
The ADC input voltage must always be greater than VSSAD and less than
VDDAD.
Connect the VDDAD pin to the same voltage potential as the VDD pin, and
connect the VSSAD pin to the same voltage potential as the VSS pin.
The VDDAD pin should be routed carefully for maximum noise immunity.
INTERNAL
DATA BUS
READ DDRBx
WRITE DDRBx
RESET
WRITE PTBx
READ PTBx
PTBx
DDRBx
PTBx
INTERRUPT
LOGIC
CHANNEL
SELECT
ADC
CLOCK
GENERATOR
CONVERSION
COMPLETE
ADC
(VADIN)
ADC CLOCK
CGMXCLK
BUS CLOCK
ADCH4–ADCH0
ADC DATA REGISTER
AIEN
COCO
DISABLE
ADC CHANNEL x
ADIV2–ADIV0
ADICLK
VOLTAGE IN