Chapter 8 Analog-to-Digital Converter (S08ADC10V1)
MC9S08SG32 Data Sheet, Rev. 7
Freescale Semiconductor
117
9.2.1
Analog Power (VDDA)
The ADC analog portion uses VDDA as its power connection. In some packages, VDDA is connected
internally to VDD. If externally available, connect the VDDA pin to the same voltage potential as VDD.
External ltering may be necessary to ensure clean VDDA for good results.
9.2.2
Analog Ground (VSSA)
The ADC analog portion uses VSSA as its ground connection. In some packages, VSSA is connected
internally to VSS. If externally available, connect the VSSA pin to the same voltage potential as VSS.
9.2.3
Voltage Reference High (VREFH)
VREFH is the high reference voltage for the converter. In some packages, VREFH is connected internally to
VDDA. If externally available, VREFH may be connected to the same potential as VDDA or may be driven
by an external source between the minimum VDDA spec and the VDDA potential (VREFH must never exceed
VDDA).
9.2.4
Voltage Reference Low (VREFL)
VREFL is the low-reference voltage for the converter. In some packages, VREFL is connected internally to
VSSA. If externally available, connect the VREFL pin to the same voltage potential as VSSA.
9.2.5
Analog Channel Inputs (ADx)
The ADC module supports up to 28 separate analog inputs. An input is selected for conversion through the
ADCH channel select bits.
9.3
Register Denition
These memory-mapped registers control and monitor operation of the ADC:
Status and control register, ADCSC1
Status and control register, ADCSC2
Data result registers, ADCRH and ADCRL
Compare value registers, ADCCVH and ADCCVL
Conguration register, ADCCFG
Pin control registers, APCTLx1
1. Number of APCTLx registers depends on the number of external analog inputs available on the device. Please refer to the
introduction of this module for external analog input assignments.