Table of Contents
Advertisement
(7) Interrupt request flag (ADIF)
The interrupt request flag (ADIF) is not cleared even if the contents of the analog input channel specification
register (ADS) are changed.
If the analog input pin is changed during conversion, therefore, the result of the A/D conversion of the preceding
analog input signal and the conversion end interrupt request flag may be set immediately before ADS is
rewritten.
If ADIF is read immediately after ADS has been rewritten, it may be set despite the fact that
conversion of the newly selected analog input signal has not been completed yet.
When stopping A/D conversion and then resuming, clear ADIF before resuming conversion.
Figure 11-9. A/D Conversion End Interrupt Generation Timing
Rewriting ADS
(ANIn conversion starts)
A/D conversion
ADCR
INTAD
Remarks 1.
n = 0, 1, ..., 11
2.
m = 0, 1, ..., 11
(8) AV
pin
DD
The AV
pin is the power supply pin of the analog circuit, and also supplies power to the input circuit of ANI0
DD
through ANI11. Even in an application where a back-up power supply is used, therefore, be sure to apply the
same voltage as the V
DD
(9) Reading A/D conversion result register (ADCR)
When the write operation is performed for the A/D converter mode register (ADM) and the analog input channel
specification register (ADS), the value of ADCR may be undefined.
termination of the conversion operation and before the write operation for ADM and ADS. If a different timing
than above is used, the conversion result may not be read properly.
316
CHAPTER 11
Rewriting ADS
(ANIm conversion starts)
ANIn
ANIn
ANIn
pin to the AV
pin as shown in Figure 11-10.
DD
Figure 11-10. Processing of AV
Main power supply
A/D CONVERTER
ADIF is set but conversion
of ANIm is not completed.
ANIm
ANIn
Pin
DD
AV
REF
V
DD
AV
DD
Back-up
capacitor
V
SS
AV
SS
Read the conversion result after the
ANIm
ANIm
ANIm
Advertisement
Table of Contents
