Conversion Data Protection Function - Fujitsu F2MC-16LX Hardware Manual

Mb90470 series 16-bit microcontroller
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CHAPTER 19 8/10-BIT A/D CONVERTER

19.4 Conversion Data Protection Function

This 8/10-bit A/D converter has a conversion data protection function to enable
continuous conversion and saving of multiple data items by µ µ µ µ DMA.
I 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 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 µDMA.
The stop is canceled after the data has been transferred by µDMA. Provided conversion data is
transferred normally, A/D conversion is performed without pausing.
I Caution when using the conversion data protection function
There is a relationship between the INT and INTE bits of ADCS2 and the operation of the
conversion data protection function.
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 in succession and older results are lost. If µDMA 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.
Clear the INT bit in this case to cancel the stop.
When interrupts are disabled during DMAC operation while A/D conversion is 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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