MC68HC908AT32 Datasheet, PDF (307/378 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 26
Analog-to-Digital Converter (ADC-15)
NOTE
This analog-to-digital converter (ADC) is for the J1850 (52-pin PLCC)
protocol only.
26.1 Introduction
This section describes the analog-to-digital converter (ADC-15). The ADC is an 8-bit analog-to-digital
converter.
26.2 Features
Features of the ADC module 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
26.3 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 15 ADC channels as ADC voltage in (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 26-1.)
26.3.1 ADC Port I/O Pins
PTD6/ATD14/TACLK–PTD0/ATD8 and PTB7/ATD7–PTB0/ATD0 are general-purpose I/O pins that
share with the ADC channels. The channel select bits 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/TACLK pin
as the clock input for the TIM.
MC68HC908AT32 Data Sheet, Rev. 3.1
Freescale Semiconductor
307