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R01UH0336EJ0102 Rev.1.02
Page 1275 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 23 A/D Converter
23.3 Functional Description
The A/D converter A (ADCAn) converts up to 18 analog input signals into
digital values and supports 10-bit and 12-bit resolution.
Note
The setting of 10-bit or 12-bit resolution is applied to all the channels. The
resolution cannot be set independently for each channel.
Channels and
channel groups
Input channels can be grouped into 3 channel groups (CG). A list of input
channels assigned to each CG is called the scan list (also applied to the
diagnostic A/D conversion of CG0). The scan list can be easily set in 1
register and re-configured during A/D conversion. The A/D conversion of all
the channels included in the scan list is called the scan list conversion.
The ADCAn supports up to 3 differently-prioritized channel groups and 2
conversion modes:
• One-shot conversion mode: When channel repeat mode is not used, the
scan list conversion is performed one time.
When channel repeat mode is used, each
channel of the scan list is performed specified
times (1 to 4).
• Continuous conversion mode: The scan list conversion is performed
repeatedly.
A/D conversion
The A/D conversion can be triggered by software or hardware.
A multiplexer selects the channel to be converted and the common sample
and hold circuit holds the input voltage.
The successive approximation register (SAR) holds the output voltage values
of the digital-to-analog converter (DAC) to be compared with the analog input
voltage values, as the 10-bit or 12-bit digital values.
After each successful conversion, the INTADCAnTLLT interrupt is generated.
A/D conversion
result registers
When the A/D conversion is complete, the contents of the SAR register are
stored in 3 registers, allowing the latest conversion results, the latest
conversion results for CGi, and the latest conversion results for channel m to
be read, respectively.
Depending on the setting, the ADCAn generates a conversion end interrupt
after the A/D conversion of certain channels and/or at the end of the A/D
conversion of all the channels of a channel group.
Conversion result
check
The ADCAn allows the A/D conversion results to be checked using the
following functions.
• Overwrite check for A/D conversion result
• Read flag for A/D conversion result
• Upper/lower limit comparison for A/D conversion result
Discharge
If required, the internal capacitor of the sample and hold circuit can be
discharged prior to every conversion.