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CHAPTER 11 A/D CONVERTER
11.1
Overview of A/D Converter
The A/D converter can be selected to function either as an 8-bit successive
approximation type A/D conversion or as a sense function. The sense function
performs a high-speed comparison between the input voltage and a set voltage. Both
functions select one input signal from the eight analog input pin channels and can be
activated either by software, by an internal clock, or by an 8/16-bit timer output.
s A/D Conversion Function
The A/D conversion function converts the analog voltage (input voltage) input to an analog input
pin to an 8-bit digital value.
Selects one input from eight analog input pins.
Conversion speed is 44 instruction cycles (41.9
s with highest main clock and 4.2 MHz
source oscillation).
Generates an interrupt when A/D conversion completes.
Conversion completion can also be determined by software.
The following methods are available to activate A/D conversion:
Activation by software
Continuous activation by a timebase timer output (divide-by-28 main clock source oscillation)
Continuous activation by an 8/16-bit timer/counter output.
s Sense Function
The sense function compares the analog voltage (input voltage) input to an analog input pin with
the voltage (compare voltage) corresponding to the value set in the A/D data register (ADCD),
and determines which voltage is higher or lower.
Selects one input from eight analog input pins.
Compare speed is 12 instruction cycles (11.4 s in main clock mode, with the highest clock
speed selected, and a clock oscillator frequency of 4.2 MHz).
Generates an interrupt when the comparison condition is satisfied.
The following methods are available to activate the sense function:
Activation by software
Continuous activation by a timebase timer output (divide-by-28 main clock source oscillation)
Continuous activation by an 8/16-bit timer/counter output.