Datasheet

Analog-to-Digital Converter (S08ATDV3)
MC9S08GT16A/GT8A Data Sheet, Rev. 1
Freescale Semiconductor 225
14.2.1 ADP7–ADP0 — Channel Input Pins
The channel pins are used as the analog input pins of the ATD. Each pin is connected to an analog switch
which serves as the signal gate into the sample submodule.
14.2.2 V
REFH
, V
REFL
— ATD Reference Pins
These pins serve as the source for the high and low reference potentials for the converter. Separation from
the power supply pins accommodates the filtering necessary to achieve the accuracy of which the system
is capable.
14.2.3 V
DDAD
, V
SSAD
— ATD Supply Pins
These two pins are used to supply power and ground to the analog section of the ATD. Dedicated power
is required to isolate the sensitive analog circuitry from the normal levels of noise present on digital power
supplies.
NOTE
V
DDAD1
and V
DD
must be at the same potential. Likewise, V
SSAD1
and V
SS
must be at the same potential.
14.3 Register Definition
The ATD has seven registers that control ATD functions.
Refer to the direct-page register summary in the memory chapter of this data sheet for the absolute address
assignments for all ATD registers. This section refers to registers and control bits only by their names. A
Freescale-provided equate or header file is used to translate these names into the appropriate absolute
addresses.
14.3.1 ATD Control (ATDC)
Writes to the ATD control register will abort the current conversion, but will not start a new conversion.
Table 14-1. Signal Properties
Name Function
AD7–AD0 Channel input pins
V
REFH
High reference voltage for ATD converter
V
REFL
Low reference voltage for ATD converter
V
DDAD
ATD power supply voltage
V
SSAD
ATD ground supply voltage