PXN20RM Datasheet, PDF (1124/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller

Analog-to-Digital Converter (ADC)
If the content of all the injected conversion mask registers is zero (i.e., no channel is selected) the interrupt
JECH is immediately issued after the start of conversion.
Once started, injected chain conversion cannot be interrupted.
34.4.1.5 Abort Conversion
Two different abort functions are provided.
The user can abort the ongoing conversion by setting the MCR[ABORT] bit. This results in a new start
pulse to the analog ADC. In the case of an abort operation, the NSTART/JSTART bit remains set and the
ABORT bit gets reset after the conversion of the next channel starts.This behavior is true for normal or
triggered/injected conversion modes.
It is also possible to abort the current chain conversion setting the MCR[ABORTCHAIN] bit. In that case
the behavior of the ADC depends on the MODE bit. If scan mode is disabled, the NSTART bit is
automatically reset together with the ABORTCHAIN bit. Otherwise, if the MODE = 1, a new chain
conversion is started.
When an ABORTCHAIN is requested while an injected conversion is running over a suspended normal
conversion, both injected chain and normal conversion chain are aborted (both NSTART and JSTART bits
are reset too).
34.4.2 Analog Clock Generator and Conversion Timings
The analog clock provided to the ADC module cannot be faster than 60 MHz and must have a 50% duty
cycle.
As shown in Figure 34-41, the analog clock generator is made up of a clock prescaler and the AD_clk
frequency is half ipg_clk frequency. When the CTU interface is enabled, depending on the position of the
rising edge of the signal ctu_trigger (coming from the CTU), AD_clk could also be stretched as described
in Figure 34-41.
ipg_clk
Clock
Prescaler
ctu_trigger
ipg_clk
ipg_clk/2
MCR[ADCLKSEL]
CTR0
CTR1
CTR2
ACKO
AD_clk
ipg_clk
AD_clk
ctu_trigger
AD_conf_latch
AD_conf_compare<1:0>
AD_conf_sample<7:0>
ipg_clk
AD_clk
ctu_trigger
ADCLKSEL = 0
ADCLKSEL = 0
Figure 34-41. Prescaler Simplified Block Diagram
34-44
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor