ROHS MC9S08QE128 Reference Manual page 201

12-bit Analog-to-Digital Converter (S08ADCV1)
10.6.2.6 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.
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 in 8-bit or 10-bit mode, or around 2 LSB in 12-bit
LSB
mode, and will increase with noise.
This error may be reduced by repeatedly sampling the input and averaging the result. Additionally the
techniques discussed in Section 10.6.2.3 will reduce this error.
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 values which are never converted for any input value.
In 8-bit or 10-bit mode, the ADC is guaranteed to be monotonic and to have no missing codes.
MC9S08QE128 MCU Series Reference Manual, Rev. 2
Freescale Semiconductor 201