RM0046 Analog-to-Digital Converter (ADC)
Doc ID 16912 Rev 5 577/936
23.3 Functional description
23.3.1 Analog channel conversion
Two conversion modes are available within the ADC:
● Normal conversion
● Injected conversion
Normal conversion
This is the normal conversion that the user programs by configuring the normal conversion
mask registers (NCMR). Each channel can be individually enabled by setting ‘1’ in the
corresponding field of NCMR registers. Mask registers must be programmed before starting
the conversion and cannot be changed until the conversion of all the selected channels
ends (NSTART bit in the Main Status Register (MSR) is reset).
Start of normal conversion
By programming the configuration bits in the Main Configuration Register (MCR), the normal
conversion can be started in two ways:
● By software — The conversion chain starts when the MCR[NSTART] bit is set.
● By trigger — An on-chip internal signal triggers an ADC conversion. The settings in the
MCR select how conversions are triggered based on these internal signals:
– A rising/falling edge detected in the signal sets the MSR[NSTART] bit and starts
the programmed conversion.
– The conversion is started if and only if the MCR[NSTART] bit is set and the
programmed level on the trigger signal is detected.
The MSR[NSTART] status bit is automatically set when the normal conversion starts. At the
same time the MCR[NSTART] bit 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.
If the content of all the normal conversion mask registers is zero (that is, no channel is
selected) the conversion operation is considered completed and the interrupt ECH (see
interrupt controller chapter for further details) is immediately issued after the start of
conversion.
Table 289. Configurations for starting normal conversion
Type of
conversion
start
NSTART
(in MCR)
NSTART
(in MSR)
Result
Software 1 1 Conversion chain starts
Trigger
—1
A falling or rising edge detected in a trigger signal sets the NSTART bit
in the MSR and starts the programmed conversion.
11
The conversion is started if the programmed level on the trigger signal
is detected: the start of conversion is enabled if the external pin is low
or high.
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