data is used by each function to determine if the right conditions have been met to assert the
associated output.
Interrupts
The digital comparator interrupt function is enabled by setting the CIE bit in the ADC Digital
Comparator Control (ADCDCCTLn) register. This bit enables the interrupt function state machine
to start monitoring the incoming ADC conversions. When the appropriate set of conditions is met,
and the DCONSSx bit is set in the ADCIM register, an interrupt is sent to the interrupt controller.
Note: For a 1 to 2 Msps rate, as the system clock frequency approaches the ADC clock frequency,
it is recommended that the application use the µDMA to store conversion data from the
FIFO to memory before processing rather than an interrupt-driven single data read. Using
the µDMA to store multiple samples before interrupting the processor amortizes interrupt
overhead across multiple transfers and prevents loss of sample data.
Note: Only a single DCONSSn bit should be set at any given time. Setting more than one of these
bits results in the INRDC bit from the ADCRIS register being masked, and no interrupt is
generated on any of the sample sequencer interrupt lines. It is recommended that when
interrupts are used, they are enabled on alternating samples or at the end of the sample
sequence.
Triggers
The digital comparator trigger function is enabled by setting the CTE bit in the ADCDCCTLn register.
This bit enables the trigger function state machine to start monitoring the incoming ADC conversions.
When the appropriate set of conditions is met, the corresponding digital comparator trigger to the
PWM module is asserted.
15.3.7.2 Operational Modes
Four operational modes are provided to support a broad range of applications and multiple possible
signaling requirements: Always, Once, Hysteresis Always, and Hysteresis Once. The operational
mode is selected using the CIM or CTM field in the ADCDCCTLn register.
Always Mode
In the Always operational mode, the associated interrupt or trigger is asserted whenever the ADC
conversion value meets its comparison criteria. The result is a string of assertions on the interrupt
or trigger while the conversions are within the appropriate range.
Once Mode
In the Once operational mode, the associated interrupt or trigger is asserted whenever the ADC
conversion value meets its comparison criteria, and the previous ADC conversion value did not.
The result is a single assertion of the interrupt or trigger when the conversions are within the
appropriate range.
Hysteresis-Always Mode
The Hysteresis-Always operational mode can only be used in conjunction with the low-band or
high-band regions because the mid-band region must be crossed and the opposite region entered
to clear the hysteresis condition. In the Hysteresis-Always mode, the associated interrupt or trigger
is asserted in the following cases: 1) the ADC conversion value meets its comparison criteria or 2)
a previous ADC conversion value has met the comparison criteria, and the hysteresis condition has
not been cleared by entering the opposite region. The result is a string of assertions on the interrupt
or trigger that continue until the opposite region is entered.
1069June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller
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