Freescale Semiconductor, Inc.
SECTION 10 ANALOG-TO-DIGITAL CONVERTER
The analog-to-digital (A/D) system, a successive approximation converter, uses an all-
capacitive charge redistribution technique to convert analog signals to digital values.
10.1 Overview
The A/D system is an 8-channel, 8-bit, multiplexed-input converter. The AV
pin is
DD
used to input supply voltage to the A/D converter. This allows the supply voltage to be
bypassed independently. The converter does not require external sample and hold cir-
cuits because of the type of charge redistribution technique used. A/D converter timing
can be synchronized to the system E clock, or to an internal resistor capacitor (RC)
oscillator. The A/D converter system consists of four functional blocks: multiplexer, an-
alog converter, digital control, and result storage. Refer to Figure 10-1.
10.1.1 Multiplexer
The multiplexer selects one of 16 inputs for conversion. Input selection is controlled by
the value of bits CD–CA in the ADCTL register. The eight port E pins are fixed-direc-
tion analog inputs to the multiplexer, and internal analog signal lines are routed to it.
ANALOG-TO-DIGITAL CONVERTER
TECHNICAL DATA
10-1
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