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CHAPTER 9 A/D CONVERTER
9.9 Precautions in Operations
(1) When 0 is written to the CE bit of the ADM0 register during conversion operations, conversion operations
stop and the conversion results are not stored in the ADCRn register (n = 0 to 7).
(2) Set the interval (input time interval) of the trigger during the external or timer trigger mode longer than
the conversion time specified by the FR2 to FR0 bits of the ADM1 register.
When interval = 0
When several triggers are input simultaneously, the analog input with the smaller ANIn pin number
is converted. The other trigger signals input simultaneously are ignored, and the number of triggers
input is not counted. Therefore, the generation of interrupts and storage of results to be stored in
the ADCRn register will become abnormal.
When 0 < interval - conversion operation time
When the timer trigger is input during the conversion operations, conversion operations are stopped
and the conversion starts according to the last timer trigger input.
When conversion operations are stopped, the conversion results are not stored in the ADCRn register.
However, the number of triggers input are counted, and when the interrupt is generated, the value
at which conversion ended is stored in the ADCRn register.
(3) Standby operations are as follows.
(a) HALT mode
Continues A/D conversion operations. When canceled by the NMI input, the ADM0 and ADM1
registers and ADCRn register hold the value.
(b) IDLE mode, STOP mode
As clock supply to the A/D converter is stopped, no conversion operations are performed. When these
modes are canceled using the NMI input, the ADM0 and ADM1 registers and the ADCRn register hold
the value. However, when the IDLE and STOP modes are set during conversion operations, the
conversion operations are stopped. At this time, if canceled using the NMI input, the conversion
operation resumes, but the conversion result written to the ADCRn register will become undefined.
In the IDLE and STOP modes, operations of the comparator are also stopped to reduce the power
consumption, and to further reduce current consumption, set the voltage of the AV
REF1
to V
SS
.