MC68HC08AS32A Datasheet, PDF (53/296 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Data Sheet — MC68HC08AS32A
Section 3. Analog-to-Digital Converter (ADC)
3.1 Introduction
This section describes the 8-bit analog-to-digital converter (ADC).
3.2 Features
Features of the ADC module include:
• 15 channels (52-PLCC) with multiplexed input
• Linear successive approximation
• 8-bit resolution
• Single or continuous conversion
• Conversion complete flag or conversion complete interrupt
• Selectable ADC clock
3.3 Functional Description
Fifteen ADC channels are available for sampling external sources at pins
PTD6/ATD14/TCLK–PTD0/ATD8 and PTB7/ATD7–PTB0/ATD0. An analog
multiplexer allows the single ADC converter to select one of the 15 ADC channels
as ADC voltage input (ADCVIN). ADCVIN is converted by the successive
approximation register-based counters. When the conversion is completed, ADC
places the result in the ADC data register and sets a flag or generates an interrupt.
See Figure 3-2.
3.3.1 ADC Port I/O Pins
PTD6/ATD14/TCLK–PTD0/ATD8 and PTB7/ATD7–PTB0/ATD0 are general-
purpose I/O pins that are shared with the ADC channels.
The channel select bits (ADC status control register, $0038), define which ADC
channel/port pin will be used as the input signal. The ADC overrides the port I/O
logic by forcing that pin as input to the ADC. The remaining ADC channels/port pins
are controlled by the port I/O logic and can be used as general-purpose I/O. Writes
to the port register or DDR will not have any affect on the port pin that is selected
by the ADC. Read of a port pin which is in use by the ADC will return a logic 0 if the
corresponding DDR bit is at logic 0. If the DDR bit is at logic 1, the value in the port
data latch is read.
NOTE: Do not use ADC channel ATD14 when using the PTD6/ATD14/TCLK pin as the
clock input for the TIM.
MC68HC08AS32A — Rev. 1
MOTOROLA
Analog-to-Digital Converter (ADC)
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Data Sheet
53