22.3.8.1 Conversion Tailgating
Scan conversions have priority over single channel conversions. This means that if scan and single triggers are received simultaneous-
ly, or even if the scan is received later when ADC is being warmed up for performing a single conversion, the scan conversion will have
priority and will be done before the single conversion. However, a scan trigger will not interrupt in the middle of a single conversion, i.e.,
if the single conversion is in the acquisition or approximation phase, then the scan will have to wait for the single conversion to com-
plete. If a scan sequence is triggered by a timer on a periodic basis, single channel conversion that started just before a scan trigger
can delay the start of the scan sequence, thus causing jitter in sample rate. To solve this, conversion tailgating can be chosen by setting
TAILGATE in ADCn_CTRL. When this bit is set, any triggered single channels will wait for the next scan sequence to finish before acti-
vating (see
Figure 22.13 ADC Conversion Tailgating on page 732
). The single channel will then follow immediately after the scan
sequence. In this way, the scan sequence will always start immediately when triggered, provided that the period between the scan trig-
gers is big enough to allow the single sample conversion that was triggered to finish before the next scan trigger arrives. Note that if
tailgating is set and a single channel conversion is triggered, it will indefinitely wait for a scan conversion before starting the single chan-
nel conversion.
SINGLESTART
SCANSTART
SCANACT
ADC action
SINGLEACT
Scan
Single
Scan
Single
Scan
Figure 22.13. ADC Conversion Tailgating
22.3.8.2 Repetitive Mode
Both single channel and scan mode can be run as a one shot conversion or in repetitive mode. The REP bitfield in ADCn_SIN-
GLECTRL/ADCn_SCANCTRL registers can be used to activate the repetitive mode for single and scan respectively. In order to achieve
the maximum sampling rate of 1 Msps, repetitive mode should be used.
EFM32JG1 Reference Manual
ADC - Analog to Digital Converter
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