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CHAPTER 17 8/10-BIT A/D CONVERTER
17.6 Conversion Data Protection Function of 8/10-Bit A/D
Converter
This 8/10-bit A/D converter has a conversion data protection function to enable
continuous conversion and saving of multiple data items by μDMAC.
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Conversion data protection function
The 8/10-bit A/D converter has only a single conversion data register. In continuous A/D
conversion, conversion data is lost when the next conversion operation ends and its result is
stored in the register. To prevent this, the A/D converter stops A/D conversion without storing a
conversion result to the register in cases when a conversion has been completed, but the result
of the previous conversion has not been transferred yet to memory via μDMAC.
The temporary stop is canceled after the conversion data has been transferred to memory by
μDMAC. Provided conversion data is transferred normally, A/D conversion continuously
performs without pausing.
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Caution when using the conversion data protection function
This function corresponds to the INT and INTE bits of ADCS2 register.
The conversion data protection function operates only in the interrupt enabled state (INTE = 1).
In interrupt disabled state (INTE = 0), this function does not operate. In continuous A/D
conversion, conversion results will be stored to the register in succession and older results are
lost. If μDMAC is not used in the interrupt enabled state (INTE = 1), the INT bit will not be
cleared and the data protection function becomes effective, stopping the operation of the 8/10-
bit A/D converter temporarily. Clear the INT bit by the interrupt sequence in this case to cancel
the stop.
When interrupts are disabled during DMA operation while A/D conversion is temporarily
stopped, data in the conversion data registers will sometimes change before A/D conversion
starts and data is transferred. Data that was stored during the stop will be lost if data conversion
is restarted during operation stop.
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