mc68hc908lv8 Freescale Semiconductor, Inc, mc68hc908lv8 Datasheet - Page 107

• Manufacturer Part Number: mc68hc908lv8
• Description: M68hc08 Microcontrollers 8-bit Microcontroller With Integrated Lcd Driver
• Manufacturer: Freescale Semiconductor, Inc

8.3.4.6 Code Jitter, Non-Monotonicity and Missing Codes
Analog-to-digital converters are susceptible to three special forms of error. These are code jitter,
non-monotonicity, and missing codes.
8.4 Interrupts
When AIEN is set, the ADC10 is capable of generating a CPU interrupt after each conversion. A CPU
interrupt is generated when the conversion completes (indicated by COCO being set). COCO will set at
the end of a conversion regardless of the state of AIEN.
8.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
8.5.1 Wait Mode
The ADC10 will continue the conversion process and will generate an interrupt following a conversion if
AIEN is set. If the ADC10 is not required to bring the MCU out of wait mode, ensure that the ADC10 is not
in continuous conversion mode by clearing ADCO in the ADC10 status and Control Register before
executing the WAIT instruction. In single conversion mode the ADC10 automatically enters a low-power
state when the conversion is complete. It is not necessary to set the channel select bits (ADCH[4:0]) to
all 1s to enter a low power state.
8.5.2 Stop Mode
If ACLKEN is clear, executing a STOP instruction will abort the current conversion and place the ADC10
in a low-power state. Upon return from stop mode, a write to ADCSC is required to resume conversions,
and the result stored in ADRH and ADRL will represent the last completed conversion until the new
conversion completes.
If ACLKEN is set, the ADC10 continues normal operation during stop mode. The ADC10 will continue the
conversion process and will generate an interrupt following a conversion if AIEN is set. If the ADC10 is
not required to bring the MCU out of stop mode, ensure that the ADC10 is not in continuous conversion
mode by clearing ADCO in the ADC10 status and Control Register before executing the STOP instruction.
In single conversion mode the ADC10 automatically enters a low-power state when the conversion is
complete. It is not necessary to set the channel select bits (ADCH[4:0]) to all 1s to enter a low-power state.
Freescale Semiconductor
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Code jitter is when, at certain points, a given input voltage converts to one of two values when
sampled repeatedly. Ideally, when the input voltage is infinitesimally smaller than the transition
voltage, the converter yields the lower code (and vice-versa). However, even very small amounts
of system noise can cause the converter to be indeterminate (between two codes) for a range of
input voltages around the transition voltage. This range is normally around ±1/2 LSB but will
increase with noise.
Non-monotonicity is defined as when, except for code jitter, the converter converts to a lower code
for a higher input voltage.
Missing codes are those which are never converted for any input value. In 8-bit or 10-bit mode, the
ADC10 is guaranteed to be monotonic and to have no missing codes.
MC68HC908LV8 Data Sheet, Rev. 2
Interrupts
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