Analog-to-Digital Converter (ADC)
15.5.1 Wait Mode
The ADC continues normal operation in 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 to logic 1’s before executing the WAIT instruction.
15.5.2 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.
15.6 I/O Signals
The ADC module has eight channels shared with port A I/O pins.
15.6.1 ADC Voltage In (V
)
ADIN
V
is the input voltage signal from one of the eight ADC channels to the ADC module.
ADIN
15.6.2 ADC Analog Power Pin (V
)
DDA
The ADC analog portion uses V
as its power pin. Connect the V
pin to the same voltage potential
DDA
DDA
as V . External filtering may be necessary to ensure clean V
for good results.
DD
DDA
NOTE
Route V
carefully for maximum noise immunity and place bypass
DDA
capacitors as close as possible to the package.
15.6.3 ADC Analog Ground Pin (V
)
SSA
The ADC analog portion uses V
as its ground pin. Connect the V
pin to the same voltage potential
SSA
SSA
as V .
SS
15.6.4 ADC Voltage Reference High Pin (V
)
REFH
V
is the power supply for setting the reference voltage V
. Connect the V
pin to the same
REFH
REFH
REFH
voltage potential as V
. There will be a finite current associated with V
(see Chapter 22 Electrical
DDA
REFH
Specifications).
NOTE
Route V
carefully for maximum noise immunity and place bypass
REFH
capacitors as close as possible to the package.
15.6.5 ADC Voltage Reference Low Pin (V
)
REFL
V
V
is the lower reference supply for the ADC. Connect the V
pin to the same voltage potential as
REFL
REFL
. There will be a finite current associated with V
(see Chapter 22 Electrical Specifications).
SSA
REFL
MC68HC908AP Family Data Sheet, Rev. 4
252
Freescale Semiconductor
FREESCALE [ Freescale ]
