Datasheet

• A write to ADC_SC2, ADC_SC3, ADC_SC4, ADC_CVH, or ADC_CVL occurs.
This indicates a mode of operation change has occurred and the current and rest of
conversions (when ADC_SC4[AFDEP] are not all 0s) are therefore invalid.
• The MCU is reset.
• The MCU enters stop mode with ADACK not enabled.
When a conversion is aborted, the contents of the data registers, ADC_RH and ADC_RL,
are not altered. However, they continue to be the values transferred after the completion
of the last successful conversion. If the conversion was aborted by a reset, ADC_RH and
ADC_RL return to their reset states.
19.4.4.4 Power control
The ADC module remains in its idle state until a conversion is initiated. If ADACK is
selected as the conversion clock source, the ADACK clock generator is also enabled.
Power consumption when active can be reduced by setting ADC_SC3[ADLPC]. This
results in a lower maximum value for f
ADCK
(see the data sheet).
19.4.4.5 Sample time and total conversion time
The total conversion time depends on the sample time (as determined by
ADC_SC3[ADLSMP]), the MCU bus frequency, the conversion mode (8-bit, 10-bit or
12-bit), and the frequency of the conversion clock (f
ADCK
). After the module becomes
active, sampling of the input begins.ADC_SC3[ADLSMP] selects between short (3.5
ADCK cycles) and long (23.5 ADCK cycles) sample times. When sampling is complete,
the converter is isolated from the input channel and a successive approximation algorithm
is performed to determine the digital value of the analog signal. The result of the
conversion is transferred to ADC_RH and ADC_RL upon completion of the conversion
algorithm.
If the bus frequency is less than the fADCK frequency, precise sample time for
continuous conversions cannot be guaranteed when short sample is enabled
(ADC_SC3[ADLSMP] = 0). If the bus frequency is less than 1/11th of the f
ADCK
frequency, precise sample time for continuous conversions cannot be guaranteed when
long sample is enabled (ADC_SC3[ADLSMP] = 1).
The maximum total conversion time for different conditions is summarized in the table
below.
Functional description
MC9S08PA60 Reference Manual, Rev. 1, 9/2012
540 Freescale Semiconductor, Inc.