M-V850E-IA4 Renesas Electronics America, M-V850E-IA4 Datasheet - Page 571

• Manufacturer Part Number: M-V850E-IA4
• Description: KIT EVAL V850E IA4 UPD70F3186
• Manufacturer: Renesas Electronics America

Specifications of M-V850E-IA4

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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13.7 Cautions
13.7.1 Writing to the ADA2CTL1 and ADA2CTL3 registers during conversion
prohibited. If data is written to the registers during A/D conversion, the conversion result of A/D2 conversion result
register n (ADA2CRn) and the conversion operation cannot be guaranteed (n = 0 to 7). To write data to the
ADA2CTL1 and ADA2CTL3 registers, be sure to stop the conversion once (ADA2CTL0.ADA2CE bit = 0), and then re-
set the conversion conditions.
13.7.2 Conflict with timing of storing data in the conversion result register
A/D2 conversion result register n (ADA2CRn) on A/D conversion end conflicts with the operations (1) to (4) are given
below.
Writing the ADA2CTL1 and ADA2CTL3 registers (including writing the same value) during A/D conversion is
Cautions when the timing of storing the A/D conversion result from the successive approximation register (SAR) to
(1) Conflict with timing of reading the ADA2CRn register
(2) Conflicts with A/D conversion end timing
If the timing of storing the A/D conversion result from the SAR register to the ADA2CRn register conflicts with
the timing of reading the ADA2CRn register, an undefined value is read from the ADA2CRn register.
Nevertheless, the conversion result is correctly stored in the ADA2CRn register.
[Countermeasures]
If the timing of storing the A/D conversion result from the SAR register to the ADA2CRn register conflicts with
the timing of stopping the A/D conversion (ADA2CTL0.ADA2CE bit = 0), an undefined value is written to the
ADA2CRn register.
[Countermeasures]
Take either of the following measures to prevent an undefined value from being read from the ADA2CRn
register.
• Immediately read the ADA2CRn register during the A/D2 conversion end interrupt (INTAD2) servicing.
• Start DMA with the A/D2 conversion end interrupt (INTAD2) and read the ADA2CRn register with DMA.
• Continuously read the ADA2CRn register twice and compare those values. If those values are the
Take either of the following measures to prevent an undefined value from being written to the ADA2CRn
register.
• Immediately set the ADA2CTL0 register to 80H or 00H during the A/D2 conversion end interrupt
• Start DMA with the A/D2 conversion end interrupt (INTAD2) and set the ADA2CTL0 register to 80H or
Even if that reading cannot immediately be performed in accordance with the interrupt priority or multiple
interrupts, read the ADA2CRn register before the next storing timing.
same, it is judged as the correct value. If those values differ, read the ADA2CRn register once more (for
a third time), and that read value is handled as the correct value. This processing must be performed
before the next conversion ends. However, if an A/D2 conversion end interrupt (INTAD2) occurs during
the series of software operations due to the third reading, repeat reading twice consecutively to check if
the values are the same.
(INTAD2) servicing.
interrupt priority or multiple interrupts, stop the A/D conversion (ADA2CTL0 register = 80H or 00H)
before the next storing timing.
00H with DMA.
Even if that writing cannot immediately be performed in accordance with the
CHAPTER 13 A/D CONVERTER 2
User’s Manual U16543EJ4V0UD
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