mc68hc908gp32 Freescale Semiconductor, Inc, mc68hc908gp32 Datasheet - Page 53

• Manufacturer Part Number: mc68hc908gp32
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 4
Analog-to-Digital Converter (ADC)
4.1 Introduction
This section describes the 8-bit analog-to-digital converter (ADC).
4.2 Features
Features of the ADC module include:
4.3 Functional Description
The ADC provides eight pins for sampling external sources at pins PTB7/AD7–PTB0/AD0. An analog
multiplexer allows the single ADC converter to select one of eight ADC channels as ADC voltage in
(V
When the conversion is completed, ADC places the result in the ADC data register and sets a flag or
generates an interrupt. (See
4.3.1 ADC Port I/O Pins
PTB7/AD7–PTB0/AD0 are general-purpose I/O (input/output) 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 in use by the ADC
will return a logic 0.
4.3.2 Voltage Conversion
When the input voltage to the ADC equals V
input voltage equals V
straight-line linear conversion.
Freescale Semiconductor
ADIN
•
•
•
•
•
•
Eight channels with multiplexed input
Linear successive approximation with monotonicity
8-bit resolution
Single or continuous conversion
Conversion complete flag or conversion complete interrupt
Selectable ADC clock
). V
ADIN
Inside the ADC module, the reference voltages V
ADC analog power, V
ground, V
analog supply voltages.
is converted by the successive approximation register-based analog-to-digital converter.
REFL
SSAD
,
the ADC converts it to $00. Input voltages between V
Figure
. Therefore, the ADC input voltage should not exceed these
MC68HC908GP32 Data Sheet, Rev. 10
4-1.)
DDAD
; and V
REFH
NOTE
REFL
, the ADC converts the signal to $FF (full scale). If the
is connected to the ADC analog
REFH
is connected to the
REFH
and V
REFL
are a
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