MC68HC908GT16_07 Datasheet, PDF (49/292 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 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:
• 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
3.3 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_ADIN). V_ADIN is converted by the successive approximation register-based analog-to-digital converter.
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
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 data
direction register (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 0.
MC68HC908GT16 • MC68HC908GT8 • MC68HC08GT16 Data Sheet, Rev. 5.0
Freescale Semiconductor
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