NEC mPD789101 User Manual page 145

CHAPTER 11 8-BIT A/D CONVERTER ( µ PD789104, 789124 SUBSERIES)
(4) Conversion results immediately following start of A/D conversion
The first A/D conversion value immediately following the start of A/D converter operation may be undefined.
Be sure to poll the A/D conversion end interrupt request (INTAD0) and perform processing such as annulling
the first conversion result.
(5) Timing that makes the A/D conversion result undefined
If the timing of the end of A/D conversion and the timing of the stop of operation of the A/C converter conflict,
the A/D conversion value may be undefined. Because of this, be sure to read out the A/D conversion result
while the A/D converter is in operation. Furthermore, when reading out an A/D conversion result after A/D
converter operation has stopped, be sure to have done so by the time the next conversion result is complete.
The conversion result readout timing is shown in Figures 11-8 and 11-9.
Figure 11-8. Conversion Result Readout Timing (When Conversion Result Is Undefined Value)
A/D conversion end
ADCR0
INTAD0
ADCS0
Normal conversion result read out
Figure 11-9. Conversion Result Readout Timing (When Conversion Result Is Normal Value)
A/D conversion end
ADCR0
INTAD0
ADCS0
A/D conversion end
Normal conversion result
A/D operation stopped
Normal conversion result
A/D operation stopped Normal conversion result read out
User's Manual U13045EJ2V0UM00
Undefined value
Undefined value read out
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