Freescale Semiconductor MCF51QE128RM manual Analog Power Vddad, Analog Ground Vssad

Analog-to-Digital Converter (S08ADC12V1)

11.2.1Analog Power (VDDAD)

The ADC analog portion uses VDDAD as its power connection. In some packages, VDDAD is connected internally to VDD. If externally available, connect the VDDAD pin to the same voltage potential as VDD. External filtering may be necessary to ensure clean VDDAD for good results.

11.2.2Analog Ground (VSSAD)

The ADC analog portion uses VSSAD as its ground connection. In some packages, VSSAD is connected internally to VSS. If externally available, connect the VSSAD pin to the same voltage potential as VSS.

11.2.3Voltage Reference High (VREFH)

VREFH is the high reference voltage for the converter. In some packages, VREFH is connected internally to VDDAD. If externally available, VREFH may be connected to the same potential as VDDAD or may be driven by an external source between the minimum VDDAD spec and the VDDAD potential (VREFH must never exceed VDDAD).

11.2.4Voltage Reference Low (VREFL)

VREFL is the low-reference voltage for the converter. In some packages, VREFL is connected internally to VSSAD. If externally available, connect the VREFL pin to the same voltage potential as VSSAD.

11.2.5Analog 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.

11.3Register Definition

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

•Configuration register, ADCCFG

•Pin enable registers, APCTL1, APCTL2, APCTL3

11.3.1Status and Control Register 1 (ADCSC1)

This section describes the function of the ADC status and control register (ADCSC1). Writing ADCSC1 aborts the current conversion and initiates a new conversion (if the ADCH bits are equal to a value other than all 1s).

MCF51QE128 MCU Series Reference Manual, Rev. 3

Freescale Semiconductor 221

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