NEC mPD780024AS Series Preliminary User's Manual page 189

CHAPTER 11 8-BIT A/D CONVERTER ( µ PD780024AS SUBSERIES)
(10) 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 11-18 and 11-19 show the timing of reading the conversion result.
Figure 11-18. Timing of Reading Conversion Result (When Conversion Result Is Undefined)
ADCR0
INTAD0
ADCS0
Figure 11-19. Timing of Reading Conversion Result (When Conversion Result Is Normal)
ADCR0
INTAD0
ADCS0
(11) 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
SS0 SS0
A/D conversion completes
Normal conversion result
Normal conversion result is read.
A/D conversion completes
A/D conversion is stopped.
at one location on the board where the voltages are stable.
Preliminary User's Manual U16035EJ1V0UM
A/D conversion completes
Undefined value
A/D conversion Undefined value
is stopped.
Normal conversion result
Normal conversion
result is read.
is read.
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