mc68hc908bd48 Freescale Semiconductor, Inc, mc68hc908bd48 Datasheet - Page 156

• Manufacturer Part Number: mc68hc908bd48
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Analog-to-Digital Converter (ADC)
12.4.2 Voltage Conversion
12.4.3 Conversion Time
12.4.4 Continuous Conversion
Data Sheet
156
NOTE:
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 an
unknown state 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.
When the input voltage to the ADC equals
signal to $FF (full scale). If the input voltage equals V
converts it to $00. Input voltage between
straight-line linear conversion. All other input voltages will result in $FF
if greater than
Input voltage should not exceed the analog supply voltages.
Twelve ADC internal clocks are required to perform one conversion. The
ADC starts a conversion on the first rising edge of the ADC internal clock
immediately following a write to the ADSCR. If the ADC internal clock is
selected to run at 1MHz, then one conversion will take 12µs to complete.
With a 1MHz ADC internal clock the maximum sample rate is 83.3kHz.
In the continuous conversion mode, the ADC continuously converts the
selected channel filling the ADC data register with new data after each
conversion. Data from the previous conversion will be overwritten
whether that data has been read or not. Conversions will continue until
the ADCO bit is cleared. The COCO bit (ADC status control register,
$005D) is set after each conversion and can be cleared by writing the
ADC status and control register or reading of the ADC data register.
Number of Bus Cycles = Conversion Time × Bus Frequency
Analog-to-Digital Converter (ADC)
Conversion Time =
------ -
2
3
V
DD
and $00 if less than V
ADC Clock Frequency
12 ADC Clock Cycles
------ -
------ -
2
3
2
3
SS
V
V
DD
DD
.
MC68HC908BD48
, the ADC converts the
and V
Freescale Semiconductor
SS
SS
, the ADC
are a
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Rev. 2.1