Chapter 23 Analog-to-Digital Converter (ADC)
MPC5602P Microcontroller Reference Manual, Rev. 4
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Freescale Semiconductor
If the content of all the injected conversion mask registers (JCMR) is zero (that is, no channel is selected)
the JECH interrupt is immediately issued after the start of conversion.
Once started, injected chain conversion cannot be interrupted by any other conversion type (it can,
however, be aborted; see
Section 23.3.1.5, Abort conversion
23.3.1.5
Abort conversion
Two different abort functions are provided.
•
The user can abort the ongoing conversion by setting the MCR[ABORT] bit. The current
conversion is aborted and the conversion of the next channel of the chain is immediately started.
In the case of an abort operation, the NSTART/JSTART bit remains set and the ABORT bit is reset
after the conversion of the next channel starts. The EOC interrupt corresponding to the aborted
channel is not generated. This behavior is true for normal or triggered/Injected conversion modes.
If the last channel of a chain is aborted, the end of chain is reported generating an ECH interrupt.
•
It is also possible to abort the current chain conversion by 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 MCR[ABORTCHAIN] bit. Otherwise, if the
scan mode is enabled, a new chain conversion is started. The EOC interrupt of the current aborted
conversion is not generated but an ECH interrupt is generated to signal the end of the chain.
When a chain conversion abort is requested (ABORTCHAIN bit is set) while an injected
conversion is running over a suspended Normal conversion, both injected chain and Normal
conversion chain are aborted (both the NSTART and JSTART bits are also reset).
23.3.2
Analog clock generator and conversion timings
The clock frequency can be selected by programming the MCR[ADCLKSEL]. When this bit is set to ‘1’
the ADC clock has the same frequency as the MC_PLL_CLK. Otherwise, the ADC clock is half of the
MC_PLL_CLK frequency. The ADCLKSEL bit can be written only in power-down mode.
When the internal divider is not enabled (ADCCLKSEL = 1), it is important that the associated clock
divider in the clock generation module is ‘1’. This is needed to ensure 50% clock duty cycle.
The direct clock should basically be used only in low power mode when the device is using only the
16 MHz fast internal RC oscillator, but the conversion still requires a 16 MHz clock (an 8 MHz clock is
not fast enough).
In all other cases, the ADC should use the clock divided by two internally.
Depending on the position of the rising edge of the signal internal trigger signal coming from the CTU, the
ADC clock could also be stretched as illustrated in