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R01UH0336EJ0102 Rev.1.02
Page 1277 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 23 A/D Converter
23.3.1
Basic Operation
This section describes the basic procedure for an A/D conversion. More
detailed descriptions are given in the following sections.
1. To optimize the start-up time after power on of the A/D converter
(ADCA0CTL1.ADCA0GPS = 1), adjust the stabilization time by modifying
the setting of stabilization counter ADCAnCNT before the A/D converter is
powered on. Refer to 23.3.15, Stabilization Control.
2. Before you enable the A/D converter (ADCAnCTL0.ADCAnCE = 1), set
power on, resolution, ADCAn clock, trigger mode, conversion mode,
interrupt generation, channel groups, channel S/H function sampling time,
channel S/H hold wait time, buffer amplifier time, discharge time and so on
in the following registers:
– ADCAnCTL0 register
– ADCAnCTL1 register
– ADCAnIOCi register
– ADCAnCGi register
– ADCAnTSELi register
– ADCAnSHCTL register
– ADCAnSMCNT register
– ADCAnSHHWCNT register
– ADCAnAMPCNT register
– ADCAnDISCNT register
3. If you want to check that the A/D conversion results are within a specified
range, enable the upper/lower limit comparison function for conversion
results of the desired channels (ADCAnCTL2.ADCAnRCKm) and specify
the lower and upper limits in ADCAnLL and ADCAnUL.
4. If you want the capacitor of the sample and hold circuit to be discharged
before sampling a new value, enable the discharge function by setting
ADCAnCTL1.ADCAnDISC to 1.
5. Enable or disable the buffer amplifier by setting ADCAnCTL1.ADCAnBPC.
If you use the channel S/H function, enable the buffer amplifier function.
6. Enable the A/D converter by setting ADCAnCTL0.ADCAnCE to 1.
If you set the stabilization counter ADCAnCNT register, the A/D converter
starts A/D conversion after the stabilization time (refer to Section 27.6.15,
A/D Converter Characteristics) is elapsed after power on. If you don't use
the stabilization counter ADCAnCNT register, enable the A/D converter
after more than power down recovery time is elapsed after power on of A/D
converter (ADCA0CTL1.ADCA0GPS=1).
7. Depending on the trigger mode configured, A/D conversion is started by
either of the following channel group-related start triggers.
– Software trigger (ADCAnTRGi.ADCAnSTTi = 1)
– Hardware trigger (input signal ADCAnTTRGi)
If the A/D conversions of multiple CGs are triggered, the order of A/D
conversions depends on the priority of the CGs.
8. The A/D conversion end interrupt INTADCAnTi is generated when the A/D
conversion of channels set in ADCAnIOCi is completed.
9. Read the results from the A/D conversion result registers ADCAnLCR,
ADCAnDBiCR, and ADCAnCmCR.
Содержание V850 Series
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