UPD78F1502AGK-GAK-AX Datasheet, PDF (432/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 10 12-BIT A/D CONVERTER (μ PD78F150xA),
10-BIT A/D CONVERTER (μ PD78F151xA)
(7) AVREFP pin input impedance
A series resistor string of several tens of kΩ is connected between the AVREFP and AVREFM (or AVSS) pins.
Therefore, if the output impedance of the reference voltage supply is high, this will result in a series connection to the
series resistor string between the AVREFP and AVREFM (or AVSS) pins, resulting in a large reference voltage (AVREF)
error of A/D converter.
(8) Interrupt request flag (ADIF)
The interrupt request flag (ADIF) is not cleared even if the analog input channel specification register (ADS) is
changed.
Therefore, if an analog input pin is changed during A/D conversion, the A/D conversion result and ADIF for the pre-
change analog input may be set just before the ADS rewrite. Caution is therefore required since, at this time, when
ADIF is read immediately after the ADS rewrite, ADIF is set despite the fact A/D conversion for the post-change
analog input has not ended.
When A/D conversion is stopped and then resumed, clear ADIF before the A/D conversion operation is resumed.
Figure 10-29. Timing of A/D Conversion End Interrupt Request Generation
ADS rewrite
(start of ANIn conversion)
ADS rewrite
(start of ANIm conversion)
ADIF is set but ANIm conversion
has not ended.
A/D conversion
ANIn
ANIn
ANIm
ANIm
ADCR
ANIn
ANIn
ANIm
ANIm
ADIF
Remark 78K0R/LF3:
n = 0 to 6, 15, m = 0 to 6, 15
78K0R/LG3, 78K0R/LH3: n = 0 to 10, 15, m = 0 to 10, 15
(9) Conversion results just after A/D conversion start
The first A/D conversion value immediately after A/D conversion starts may not fall within the rating range if the ADCS
bit is set to 1 within 1 μs after the ADCE bit was set to 1, or if the ADCS bit is set to 1 with the ADCE bit = 0. Take
measures such as polling the A/D conversion end interrupt request (INTAD) and removing the first conversion result.
R01UH0004EJ0501 Rev.5.01
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Jun 20, 2011