MC68HC08AZ32A Datasheet, PDF (53/312 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Chapter 3
Analog-to-Digital Converter (ADC) Module
3.1 Introduction
This section describes the 8-bit analog-to-digital converter (ADC) module.
3.2 Features
Features include:
• 15 channels 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/TACLK–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/TACLK–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 and 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 0 if the corresponding
DDR bit is at 0. If the DDR bit is at 1, the value in the port data latch is read.
NOTE
Do not use ADC channels ATD14 or ATD12 when using the
PTD6/ATD14/TACLK or PTD4/ATD12/TBCLK pins as the clock inputs for
the 16-bit timers.
MC68HC08AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
53