TC1784
Analog to Digital Converter (ADC)
User´s Manual
23-10
V1.1, 2011-05
ADC, V1.3
23.1.7
Interrupt Structure
Each ADC kernel provides 8 independent service request output signals
(ADCx_SR[7:0]) used for interrupt handling. The interrupt generation inside the ADC
kernel is based on three different types of events.
•
Channel events:
A channel event is detected if a conversion is finished and the conversion result is
within a programmable value range.
This type of event can be used to check if analog input values are inside or out of a
nominal operating range, especially to reduce CPU load for background tasks. This
allows the user to interrupt the CPU only if the specified conversion result range is
met (or not met) instead of comparing each result by SW.
•
Result events:
A result event is detected if a new result is available in a result register and can be
read out, e.g. to store the data in memory for further treatment by SW.
This type of event can be used to trigger a read action by the CPU (or DMA).
Especially when using data reduction or digital anti-aliasing filtering, not all finished
conversion leads to a new result. Furthermore, when using a result FIFO, a result
event decouples the CPU (DMA) read out from the channel events and tolerates a
higher interrupt latency. The result register structure allows to use a single DMA
channel for a complete auto-scan sequence by triggering the read out by a result
event (if the conversion results of all channels taking part in the auto-scan sequence
target the same result register, e.g. with FIFO mechanism or with a wait-for-read
condition to avoid data loss).
•
Request source events:
A request source event is detected if a scan source has completely finished the
requested conversion sequence. For a sequential source, the user can define where
inside a conversion sequence a request source event is generated.
This type of event can be used to inform the CPU that a conversion sequence has
reached a defined state and SW can start the treatment of the related results in a
block.
Each ADC event is indicated by a dedicated flag that can be cleared by SW. An interrupt
can be generated (if enabled) for each event, independently from the status of the
corresponding event indication flag. This structure ensures efficient DMA handling of
ADC events (the ADC event can generate an interrupt without the need to clear the
indication flag). A node pointer mechanism allows the user to group interrupts events by
selecting which service request output signals SRx becomes activated by which event.
Each ADC event can be individually directed to one of the service request output signals
to adapt easily to application needs.
Note: A conversion can lead to three interrupts, one of each type. In this case, the ADC
module first triggers the request source event interrupt, then the channel event
interrupt, followed by the result event interrupt (all within a few f
ADC
clock cycles).
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