
CHAPTER 13 A/D CONVERTER
User
’
s Manual U15862EJ3V0UD
429
13.5.2 Conversion operation (software trigger mode)
Setting ADCS of the A/D converter mode register (ADM) to 1 starts conversion of the signal input to the channel
specified with the analog input channel specification register (ADS). Upon completion of the conversion, the
conversion result is stored to the ADCR register and a new conversion starts.
If ADM, ADS, the power fail comparison threshold value register (PFT), or the power fail comparison mode
register (PFM) is written to during conversion, conversion is interrupted and the conversion operation starts
again from the beginning.
If ADCS is set to 0 during conversion, conversion is interrupted and the conversion operation is stopped.
For whether or not the conversion end interrupt request signal (INTAD) is generated, refer to
13.5.3 Power fail
monitoring function
.
13.5.3 Power fail monitoring function
The conversion end interrupt request signal (INTAD) can be controlled as follows using the PFM and PFT
registers.
If PFEN = 0, INTAD is generated each time conversion ends.
If PFEN = 1 and PFCM = 0, the conversion result and the value of the PFT register are compared when
conversion ends, and INTAD is output only if ADCRH
≥
PFT.
If PFEN and PFCM = 1, the conversion result and the value of the PFT register are compared when conversion
ends and INTAD is output only if ADCRH < PFT.
Because, when PFEN = 1, the conversion result is overwritten after INTAD has been output, unless the
conversion result is read by the time the next conversion ends, in some cases it may appear as if the actual
operation differs from the operation described above (refer to
Figure 13-4
).
Figure 13-4. Power Fail Monitoring Function (PFCM = 0)
Conversion operation
ADCRH
PFT
INTAD
ANI0
80H
80H
7FH
80H
ANI0
ANI0
ANI0
Note
Note
If reading is not performed during this interval, the conversion result changes to the next conversion result.