TM4C1231H6PM Datasheet, PDF (768/1146 Pages) Texas Instruments – Tiva™ TM4C1231H6PM Microcontroller

Analog-to-Digital Converter (ADC)
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.
13.3.2
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
■ Sample phase control
■ Module clocking
Most of the ADC control logic runs at the ADC clock rate of 16 MHz. The internal ADC divider is
configured for 16-MHz operation automatically by hardware when the system XTAL is selected with
the PLL.
13.3.2.1
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
signals; and the ADC Interrupt Status and Clear (ADCISC) register, which shows active interrupts
that are enabled by the ADCIM register. Sequencer interrupts are cleared by writing a 1 to the
corresponding IN bit in ADCISC. Digital comparator interrupts are cleared by writing a 1 to the ADC
Digital Comparator Interrupt Status and Clear (ADCDCISC) register.
13.3.2.2
DMA Operation
DMA may be used to increase efficiency by allowing each sample sequencer to operate independently
and transfer data without processor intervention or reconfiguration. The ADC module provides a
request signal from each sample sequencer to the associated dedicated channel of the μDMA
controller. The ADC does not support single transfer requests. A burst transfer request is asserted
when the interrupt bit for the sample sequence is set (IE bit in the ADCSSCTLn register is set).
The arbitration size of the μDMA transfer must be a power of 2, and the associated IE bits in the
ADCSSCTLn register must be set. For example, if the μDMA channel of SS0 has an arbitration
768
June 12, 2014
Texas Instruments-Production Data