MC68HC08AS32A — Rev. 1
Data Sheet
MOTOROLA
Analog-to-Digital Converter (ADC)
For More Information On This Product,
Go to: www.freescale.com
53
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.
F
Freescale Semiconductor, Inc.
n
.