running, then the CMU automatically turns it on when the ADC sends a clock request. In such a case, it takes (7 ADC_CLK the
oscillator startup time) for the ADC_CLK to start. The oscillator startup time can be found in the device data sheet.
When triggering repeat mode using PRS and then stopping the triggered mode using STOP command, ensure that the PRS pulse used
to generate the repeat mode has gone low by the time the STOP command is issued. If the PRS pulse continues to stay high after ADC
has stopped the ongoing conversion, then it will be picked as a new trigger to start a new conversion.
Note:
The conversion settings should not be changed while the ADC is running. Doing so may lead to unpredictable behavior.
The adc_clk_sar phase is always reset by a conversion trigger as long as a conversion is not in progress. This gives predictable latency
from the time of the trigger to the time the conversion starts, regardless of when in the trigger occurs.
Software and LESENSE should not trigger conversions if PRS Timed mode is selected and PRSEN is set to 1 in the ADCn_SIN-
GLECTRL/ADCn_SCANCTRL register.
If the PRS Timed mode is being used, the acquisition time (AT) must be set greater than 0.
Scan conversions can be triggered using LESENSE as well. LESENSE only triggers one input conversion at a time (not the whole se-
quence of 32 possible inputs). The input to be converted using LESENSE must be configured by the user in the ADCn_SCANINPUT-
SEL register before triggering the conversion, i.e., one of the 32 inputs chosen in the ADCn_SCANINPUTSEL register must be the one
that is to be converted using LESENSE. The ADCn_SCANMASK is not used for LESENSE triggered conversions. Instead, the user can
select which input should be converted through LESENSE inside the LESENSE settings (LESENSE_CHX). The results of LESENSE
triggered conversions are not loaded in the FIFO/ DATA registers but are instead available in the LESENSE register. Similarly, the
SCAN interrupt flag is not set on completion of a LESENSE triggered conversion (because that flag is set only when the data is written
to the Scan FIFO). When there is a LESENSE triggered conversion going on or pending, the SCANACT status flag is set. The SCAN-
PEND interrupt flag is set when a software/PRS triggered scan goes pending because a LESENSE triggered scan is running
(software/PRS triggered scan will start after the currently running LESENSE scan conversion completes). Similarly, SCANEXTPEND
interrupt flag is set when the LESENSE triggered scan conversion goes pending because a software/PRS triggered scan is running.
LESENSE triggered conversions can be stopped at any time using the SCANSTOP command in the ADCn_CMD register. Note that the
LESENSE triggered conversion cannot trigger the Scan repeat mode.
The DBGHALT bit-field in the ADCn_CTRL register can be used to choose the ADC behavior in debug mode. If this bit is set to 1, then
in debug mode ADC completes the current conversions and then halts. This means that all conversion triggers that were received be-
fore the debug halt occurred will be serviced before the ADC halts. All conversion triggers received after the ADC was halted, will be
serviced when the debug mode is not halted any more. If the repetitive mode is running (in repetitive mode ADC keeps doing conver-
sions until the user sends a software STOP) and a debug mode halt occurs, then the ADC will gracefully complete the current on-going
conversion and then halt. The repetitive mode conversions will restart as soon as the debug mode is not halted any more.
Reference Manual
ADC - Analog to Digital Converter
silabs.com
| Building a more connected world.
Rev. 1.1 | 863