Analog-to-Digital Converter (ADC)
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor 34-43
In both modes, at the end of each conversion an End Of Conversion (EOC) interrupt is issued (if enabled
by the corresponding mask bit) and at the end of the conversion sequence an End Of Chain (ECH) interrupt
is issued (if enabled by the corresponding mask bit).
34.4.1.4 Injected Channel Conversion
A conversion chain can be injected into the ongoing normal conversion by configuring the JCMRn
injected mask registers. As in normal conversion, each internal channel can be individually selected. This
injected conversion can only be in one-shot mode and interrupts the normal conversion. When an injected
conversion is inserted, ongoing channel conversion is aborted and the injected channel request is
processed. After the last channel in the injected chain is converted, normal conversion resumes from the
channel at which the normal conversion was aborted as shown in Figure 34-40.
Figure 34-40. Injected Sample/Conversion Sequence
The ADC input signal “injection_trg” must be connected to the PIT_2 output. This allows the application
to use PIT_2 to periodically inject conversion chains. The ADC can also be externally triggered from
external inputs. See pin muxing for details.
The injected conversion can be started using two options:
• By software setting the MCR[JSTART] bit; the current conversion is suspended and the injected
chain is converted. At the end of the chain, the MSR[JSTART] bit is reset and the normal chain
conversion is resumed.
• By an external trigger signal setting the MCR[JTRGEN] bit; a programmed event (rising/falling
edge depending on MCR[JEDGE] bit) on the injection external pin starts the injected conversion
by setting the JSTART bit. At the end of the chain, the MSR[JSTART] bit is reset and the normal
chain conversion is resumed.
The JSTART status bit of MSR is automatically set when the injected conversion starts. At the same time
JSTART bit of MCR is reset, allowing the software to program a new start of conversion. In that case the
new requested conversion starts after the running conversion is completed.
At the end of each injected conversion, an End Of Injected Conversion (JEOC) interrupt is issued (if
enabled by the corresponding mask bit) and at the end of the sequence an End Of Injected Chain (JECH)
interrupt is issued (if enabled by the corresponding mask bit).
Sample B Convert B Sample C Convert C Sample D Convert D Sample E Convert E
Sample C Abort C Sample I Convert I Sample J Convert J Sample C Convert C
Injected conversion of channels I and J
Normal conversion resumes from the last
aborted channel.
The ongoing channel conversion is interrupted and the injected conversion
chain is processed first. After the injected chain is converted the normal
conversion resumes from the channel at which normal conversion was
aborted.
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