SAM4L Datasheet, PDF (846/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
Table 31-3. Event Propagation Latency
Generator
CHMXi.EVMX
Input Glitch Filter
EVSj.IGF
Software event
-
Generator without Event Shaper
-
Generator with Event Shaper
Off
Generator with Event Shaper
On
Asynchronous Generator in
SleepWalking™ operation
On or Off
Latency
0
0
2
3 * 2^IGFDR
unpredicted
Clock
-
-
CLK_PEVC
CLK_RCSYS
-
Refer to the Module Configuration section at the end of this chapter for the list of generators
implementing Event Shapers.
31.7
Application Example
This application example shows how the Peripheral Event System can be used to program the
ADC Interface to perform ADC conversions at selected intervals.
One of the possible ADC conversion trigger is a peripheral event trigger, allowing the Peripheral
Event System to synchronize conversion with some configured peripheral event source. One
particular peripheral event source can be an AST peripheral event, among other types of periph-
eral events. The Peripheral Event System can then be used to set up the ADC Interface to
sample an analog signal at regular intervals generated by the AST.
The user must enable peripheral events in the AST and in the ADC Interface. Refer to the corre-
sponding chapters for how this is accomplished. Next, the AST will generate peripheral events
periodically, and the Peripheral Event System will route the peripheral events to the ADC Inter-
face, which will perform ADC conversions at the selected intervals.
Figure 31-4. Application Example
Periodic peripheral
AST ^event
Peripheral
Event
System
Trigger
conversion
ADC
Interface
Since the AST peripheral event is an asynchronous event, the description above will also work
in Power Save Modes where the ADC clock is stopped. In this case, the ADC clock (and clock
source, if needed) will be restarted during the ADC conversion. After the conversion, the ADC
clock and clock source will return to the sleep state, unless the ADC generates an interrupt,
which in turn will wake up the system. Using asynchronous events thus allows ADC operation in
much lower power states than would otherwise be possible.
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