MC908MR16CFUE Datasheet, PDF (47/282 Pages) Freescale Semiconductor, Inc – On-chip programming firmware for use with host personal computer, Clock generator module (CGM)

INTERNAL
DATA BUS
READ PTB/PTC
ADC DATA REGISTERS
Functional Description
PTB/Cx
ADC CHANNEL x
DISABLE
CONVERSION
INTERRUPT
COMPLETE
ADC
LOGIC
ADC VOLTAGE IN
ADVIN
CHANNEL
SELECT
ADCH[4:0]
AIEN
COCO
ADC CLOCK
CGMXCLK
BUS CLOCK
CLOCK
GENERATOR
ADIV[2:0]
ADICLK
Figure 3-2. ADC Block Diagram
3.3.1 ADC Port I/O Pins
PTC1/ATD9:PTC0/ATD8 and PTB7/ATD7:PTB0/ATD0 are general-purpose 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 logic when that port is selected by the ADC multiplexer. The remaining ADC
channels/port pins are controlled by the port logic and can be used as general-purpose input/output (I/O)
pins. 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 0.
3.3.2 Voltage Conversion
When the input voltage to the ADC equals V_REFH, the ADC converts the signal to $3FF (full scale). If the
input voltage equals V_REFL, the ADC converts it to $000. Input voltages between V_REFH and V_REFL are
straight-line linear conversions. All other input voltages will result in $3FF if greater than V_REFH and $000
if less than V_REFL.
NOTE
Input voltage should not exceed the analog supply voltages. See
19.13 Analog-to-Digital Converter (ADC) Characteristics.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
47