MC68HC908KX8 Datasheet, PDF (246/310 Pages) Motorola, Inc – Microcontrollers

Analog-to-Digital Converter (ADC)
17.3 Features
Features of the ADC module include:
• Four channels with multiplexed input
• Linear successive approximation
• 8-bit resolution
• Single or continuous conversion
• Conversion complete flag or conversion complete interrupt
• Selectable ADC clock
17.4 Functional Description
The ADC provides four pins for sampling external sources at pins
PTB3–PTB0. An analog multiplexer allows the single ADC converter to
select one of four 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 17-1.
The MC68HC908KX8 uses V_DD as the high voltage reference.
17.4.1 ADC Port I/O Pins
PTB3–PTB0 are general-purpose input/output (I/O) pins that are shared
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 effect 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.
Technical Data
246
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
Analog-to-Digital Converter (ADC)
MOTOROLA