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CHAPTER 13 10-BIT A/D CONVERTER ( µ PD780354, 780354Y SUBSERIES)
(11) Timing at which A/D conversion result is undefined
The A/D conversion value may be undefined if the timing of completion of A/D conversion and the timing of
stopping the A/D conversion conflict with each other. Therefore, read the A/D conversion result during the A/
D conversion operation. To read the conversion result after stopping the A/D conversion operation, be sure to
stop the A/D conversion before the next conversion ends.
Figures 13-18 and 13-19 show the timing of reading the conversion result.
Figure 13-18. Timing of Reading Conversion Result (When Conversion Result Is Undefined)
ADCR0
INTAD0
ADCS0
Figure 13-19. Timing of Reading Conversion Result (When Conversion Result Is Normal)
ADCR0
INTAD0
ADCS0
(12) Notes on board design
Locate analog circuits as far away from digital circuits as possible on the board because the analog circuits may
be affected by the noise of the digital circuits. In particular, do not cross an analog signal line with a digital signal
line, or wire an analog signal line in the vicinity of a digital signal line. Otherwise, the A/D conversion
characteristics may be affected by the noise of the digital line.
Connect AV
and V
SS
SS1
262
A/D conversion ends
Normal conversion result
Normal conversion
result is read.
A/D conversion ends
A/D conversion is
stopped.
at one location on the board where the voltages are stable.
User's Manual U15798EJ2V0UD
A/D conversion ends
Undefined value
A/D conversion is
stopped.
Normal conversion result
Normal conversion
result is read.
Undefined
value is read.
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