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CHAPTER 18 8/10-BIT A/D CONVERTER
18.6.2
A/D conversion data protection function
When A/D conversion is performed in the interrupt enabled state, the conversion data
protection function operates.
■ A/D Conversion Data Protection Function
The A/D converter has just one data register that holds conversion data. When a single A/D conversion is
completed, the data in the data register is rewritten.
If the conversion data were not transferred to memory before the next conversion data was stored, part of
the conversion data would be lost. The data protection function operates in the interrupt enabled state
(INTE = 1), as described below, to prevent loss of data.
●
Data protection function when EI
When conversion data is stored in the A/D data register (ADCR), the INT bit of the A/D control status
register1 (ADCS1) is set to "1".
While the INT bit is "1", A/D conversion is halted.
Halt status is released when the INT bit is cleared after data in the A/D data register (ADCR) has been
transferred to memory by the interrupt routine.
●
Data protection function when EI
In continuous conversion using EI
"1" when a conversion ends. This status continues until EI
from the data register to memory. In the meantime, the A/D conversion is halted, and the next conversion
data is not stored. When the data transfer to memory is completed, conversion resumes, but once PAUS bit
is set, it is not cleared by itself, write "0" to clear PAUS bit.
Figure 18.6-3 shows operation flowchart of the data protection function when EI
298
2
OS is not used
2
OS is used
2
OS, the PAUS bit of the A/D control status register1 (ADCS1) is kept at
2
OS finishes transferring the conversion data
2
OS is used.
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