For a given sample sequence, each sample is defined by bit fields in the ADC Sample Sequence
Input Multiplexer Select (ADCSSMUXn), ADC Sample Sequence Extended Input Multiplexer
Select (ADCSSEMUXn) and ADC Sample Sequence Control (ADCSSCTLn) registers, where
"n" corresponds to the sequence number. The ADCSSMUXn and ADCSSEMUXn fields select the
input pin, while the ADCSSCTLn fields contain the sample control bits corresponding to parameters
such as temperature sensor selection, interrupt enable, end of sequence, and differential input
mode. Sample sequencers are enabled by setting the respective ASENn bit in the ADC Active
Sample Sequencer (ADCACTSS) register and should be configured before being enabled. Sampling
is then initiated by setting the SSn bit in the ADC Processor Sample Sequence Initiate (ADCPSSI)
register. In addition, sample sequences may be initiated on multiple ADC modules simultaneously
using the GSYNC and SYNCWAIT bits in the ADCPSSI register during the configuration of each ADC
module. For more information on using these bits, refer to page 1103.
When configuring a sample sequence, multiple uses of the same input pin within the same sequence
are allowed. In the ADCSSCTLn register, the IEn bits can be set for any combination of samples,
allowing interrupts to be generated after every sample in the sequence if necessary. Also, the END
bit can be set at any point within a sample sequence. For example, if Sequencer 0 is used, the END
bit can be set in the nibble associated with the fifth sample, allowing Sequencer 0 to complete
execution of the sample sequence after the fifth sample.
After a sample sequence completes execution, the result data can be retrieved from the ADC
Sample Sequence Result FIFO (ADCSSFIFOn) registers. The FIFOs are simple circular buffers
that read a single address to "pop" result data. For software debug purposes, the positions of the
FIFO head and tail pointers are visible in the ADC Sample Sequence FIFO Status (ADCSSFSTATn)
registers along with FULL and EMPTY status flags. If a write is attempted when the FIFO is full, the
write does not occur and an overflow condition is indicated. Overflow and underflow conditions are
monitored using the ADCOSTAT and ADCUSTAT registers.
15.3.2 Module Control
Outside of the sample sequencers, the remainder of the control logic is responsible for tasks such
as:
■ Interrupt generation
■ DMA operation
■ Sequence prioritization
■ Trigger configuration
■ Comparator configuration
■ External voltage reference
■ Sample phase control
■ Module clocking
15.3.2.1 Interrupts
The register configurations of the sample sequencers and digital comparators dictate which events
generate raw interrupts, but do not have control over whether the interrupt is actually sent to the
interrupt controller. The ADC module's interrupt signals are controlled by the state of the MASK bits
in the ADC Interrupt Mask (ADCIM) register. Interrupt status can be viewed at two locations: the
ADC Raw Interrupt Status (ADCRIS) register, which shows the raw status of the various interrupt
1057June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller
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