CC1110Fx / CC1111Fx
13.10.2.3 ADC Conversion Sequences
The ADC will perform sequence of
sequence, a Timer 1 channel 0 compare
event, or ADCCON1.STis 1.
a
conversions, and the results can be moved to
memory (through DMA) without any interaction
from the CPU.
ADCCON2.SREFis used to select the reference
voltage. The reference voltage should only be
changed when no conversion is running.
The ADCCON2.SCH register bits are used to
define an ADC conversion sequence from the
ADC inputs. If some of the inputs in this
sequence are not configured to be analog
input signals in the ADCCFGregister, these will
be skipped. For differential inputs both input
pins must be configured to be analog input
signals.
The ADCCON2.SDIVbits select the decimation
rate (and thereby also the resolution and time
required to complete a conversion and sample
rate). The decimation rate should only be
changed when no conversion is running.
The ADCCON2.SCH register bits are used to
define an ADC conversion sequence.
The ADC can be programmed to perform a
single conversion (single-ended, differential,
GND, internal voltage reference, temperature
sensor, or VDD/3). This is called an extra
conversion and is controlled with the ADCCON3
register. This conversion is triggered by writing
to ADCCON3. If this register is written while the
ADC is running, the conversion will take place
as soon as the sequence has completed. If the
register is written while the ADC is not running,
the conversion will take place immediately
after the ADCCON3register is updated.
• 0000 ≤ ADCCON2.SCH ≤ 0111: Single-
ended inputs
• 1000
≤
ADCCON2.SCH
≤
1011:
Differential inputs
• 1100 ≤ ADCCON2.SCH ≤ 1111: GND,
internal voltage reference, temp. sensor,
and VDD/3
When ADCCON2.SCH is set to a value less
than 1000 a conversion sequence will contain
a conversion from each ADC input, starting at
AIN0 and ending at the input programmed in
ADCCON2.SCH.When ADCCON2.SCHis set to
a value ranging from 1000 to 1011, the
sequence will start at the differential input pair
(AIN0 – AIN1) and stop at the input pair given
by ADCCON2.SCH. For even higher settings,
only single conversions are performed. In
addition to this sequence of conversions, the
ADC can be programmed to perform a single
conversion (see next section).
The ADCCON3 register controls which input to
use, reference voltage, and decimation rate for
the extra conversion. The coding of the
register bits is exactly as for ADCCON2.
Note: If a sequence of conversions is
started without setting any of the P0 pins
as analog inputs, ADCCON2.SCH and
ADCCON1.EOC will still be updated, as if
the conversions had taken place.
13.10.2.4 ADC Operating Modes
This section describes the operating modes
and initialization of conversions.
13.10.2.5 ADC Reference Voltage
The positive reference voltage for analog-to-
digital conversions is selectable as either an
internally generated 1.25 V voltage, the VDD
on AVDD pin, an external voltage applied to
the AIN7 input pin, or a differential voltage
applied to the AIN6 - AIN7 inputs (AIN6 must
have the highest input voltage). It is possible to
select the reference voltage as the input to the
ADC in order to perform a conversion of the
reference voltage e.g. for calibration purposes.
Similarly, it is possible to select the ground
terminal GND as an input.
The ADC has three control registers:
ADCCON1, ADCCON2, and ADCCON3. These
registers are used to configure the ADC and to
report status.
The ADCCON1.EOCbit is a status bit that is set
high when a conversion ends and cleared
when ADCHis read.
The ADCCON1.ST bit is used to start a
sequence of conversions. A sequence will start
when
this
bit
is
set
high,
ADCCON1.STSEL=11, and no conversion is
currently running. When the sequence is
completed, this bit is automatically cleared.
Note: P0_6 and P0_7 do not exist on
CC1111Fx, hence it is not possible to use
external voltage reference for the ADC on
the CC1111Fx.
The ADCCON1.STSEL bits select which event
that will start a new sequence of conversions.
The options which can be selected are rising
edge on external pin P2_0, end of previous
SWRS033E
Page 142 of 239
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